We might have many disabled memory regions, making the 'info mtree'
output too verbose to be useful.
Remove the disabled regions in the default output, but allow the
monitor user to display them using the '-D' option.

Before:

  (qemu) info mtree
  memory-region: system
    0000000000000000-ffffffffffffffff (prio 0, i/o): system
      0000000000000000-0000000007ffffff (prio 0, ram): alias ram-below-4g @pc.ram 0000000000000000-0000000007ffffff
      0000000000000000-ffffffffffffffff (prio -1, i/o): pci
        00000000000a0000-00000000000bffff (prio 1, i/o): vga-lowmem
        00000000000c0000-00000000000dffff (prio 1, rom): pc.rom
        00000000000e0000-00000000000fffff (prio 1, rom): alias isa-bios @pc.bios 0000000000020000-000000000003ffff
        00000000fffc0000-00000000ffffffff (prio 0, rom): pc.bios
      00000000000a0000-00000000000bffff (prio 1, i/o): alias smram-region @pci 00000000000a0000-00000000000bffff
      00000000000c0000-00000000000c3fff (prio 1, ram): alias pam-ram @pc.ram 00000000000c0000-00000000000c3fff [disabled]
      00000000000c0000-00000000000c3fff (prio 1, ram): alias pam-pci @pc.ram 00000000000c0000-00000000000c3fff [disabled]
      00000000000c0000-00000000000c3fff (prio 1, ram): alias pam-rom @pc.ram 00000000000c0000-00000000000c3fff [disabled]
      00000000000c0000-00000000000c3fff (prio 1, i/o): alias pam-pci @pci 00000000000c0000-00000000000c3fff
      00000000000c4000-00000000000c7fff (prio 1, ram): alias pam-ram @pc.ram 00000000000c4000-00000000000c7fff [disabled]
      00000000000c4000-00000000000c7fff (prio 1, ram): alias pam-pci @pc.ram 00000000000c4000-00000000000c7fff [disabled]
      00000000000c4000-00000000000c7fff (prio 1, ram): alias pam-rom @pc.ram 00000000000c4000-00000000000c7fff [disabled]
      00000000000c4000-00000000000c7fff (prio 1, i/o): alias pam-pci @pci 00000000000c4000-00000000000c7fff
      00000000000c8000-00000000000cbfff (prio 1, ram): alias pam-ram @pc.ram 00000000000c8000-00000000000cbfff [disabled]
      00000000000c8000-00000000000cbfff (prio 1, ram): alias pam-pci @pc.ram 00000000000c8000-00000000000cbfff [disabled]
      00000000000c8000-00000000000cbfff (prio 1, ram): alias pam-rom @pc.ram 00000000000c8000-00000000000cbfff [disabled]
      00000000000c8000-00000000000cbfff (prio 1, i/o): alias pam-pci @pci 00000000000c8000-00000000000cbfff
      00000000000cc000-00000000000cffff (prio 1, ram): alias pam-ram @pc.ram 00000000000cc000-00000000000cffff [disabled]
      00000000000cc000-00000000000cffff (prio 1, ram): alias pam-pci @pc.ram 00000000000cc000-00000000000cffff [disabled]
      00000000000cc000-00000000000cffff (prio 1, ram): alias pam-rom @pc.ram 00000000000cc000-00000000000cffff [disabled]
      00000000000cc000-00000000000cffff (prio 1, i/o): alias pam-pci @pci 00000000000cc000-00000000000cffff
      00000000000d0000-00000000000d3fff (prio 1, ram): alias pam-ram @pc.ram 00000000000d0000-00000000000d3fff [disabled]
      00000000000d0000-00000000000d3fff (prio 1, ram): alias pam-pci @pc.ram 00000000000d0000-00000000000d3fff [disabled]
      00000000000d0000-00000000000d3fff (prio 1, ram): alias pam-rom @pc.ram 00000000000d0000-00000000000d3fff [disabled]
      00000000000d0000-00000000000d3fff (prio 1, i/o): alias pam-pci @pci 00000000000d0000-00000000000d3fff
      00000000000d4000-00000000000d7fff (prio 1, ram): alias pam-ram @pc.ram 00000000000d4000-00000000000d7fff [disabled]
      00000000000d4000-00000000000d7fff (prio 1, ram): alias pam-pci @pc.ram 00000000000d4000-00000000000d7fff [disabled]
      00000000000d4000-00000000000d7fff (prio 1, ram): alias pam-rom @pc.ram 00000000000d4000-00000000000d7fff [disabled]
      00000000000d4000-00000000000d7fff (prio 1, i/o): alias pam-pci @pci 00000000000d4000-00000000000d7fff
      00000000000d8000-00000000000dbfff (prio 1, ram): alias pam-ram @pc.ram 00000000000d8000-00000000000dbfff [disabled]
      00000000000d8000-00000000000dbfff (prio 1, ram): alias pam-pci @pc.ram 00000000000d8000-00000000000dbfff [disabled]
      00000000000d8000-00000000000dbfff (prio 1, ram): alias pam-rom @pc.ram 00000000000d8000-00000000000dbfff [disabled]
      00000000000d8000-00000000000dbfff (prio 1, i/o): alias pam-pci @pci 00000000000d8000-00000000000dbfff
      00000000000dc000-00000000000dffff (prio 1, ram): alias pam-ram @pc.ram 00000000000dc000-00000000000dffff [disabled]
      00000000000dc000-00000000000dffff (prio 1, ram): alias pam-pci @pc.ram 00000000000dc000-00000000000dffff [disabled]
      00000000000dc000-00000000000dffff (prio 1, ram): alias pam-rom @pc.ram 00000000000dc000-00000000000dffff [disabled]
      00000000000dc000-00000000000dffff (prio 1, i/o): alias pam-pci @pci 00000000000dc000-00000000000dffff
      00000000000e0000-00000000000e3fff (prio 1, ram): alias pam-ram @pc.ram 00000000000e0000-00000000000e3fff [disabled]
      00000000000e0000-00000000000e3fff (prio 1, ram): alias pam-pci @pc.ram 00000000000e0000-00000000000e3fff [disabled]
      00000000000e0000-00000000000e3fff (prio 1, ram): alias pam-rom @pc.ram 00000000000e0000-00000000000e3fff [disabled]
      00000000000e0000-00000000000e3fff (prio 1, i/o): alias pam-pci @pci 00000000000e0000-00000000000e3fff
      00000000000e4000-00000000000e7fff (prio 1, ram): alias pam-ram @pc.ram 00000000000e4000-00000000000e7fff [disabled]
      00000000000e4000-00000000000e7fff (prio 1, ram): alias pam-pci @pc.ram 00000000000e4000-00000000000e7fff [disabled]
      00000000000e4000-00000000000e7fff (prio 1, ram): alias pam-rom @pc.ram 00000000000e4000-00000000000e7fff [disabled]
      00000000000e4000-00000000000e7fff (prio 1, i/o): alias pam-pci @pci 00000000000e4000-00000000000e7fff
      00000000000e8000-00000000000ebfff (prio 1, ram): alias pam-ram @pc.ram 00000000000e8000-00000000000ebfff [disabled]
      00000000000e8000-00000000000ebfff (prio 1, ram): alias pam-pci @pc.ram 00000000000e8000-00000000000ebfff [disabled]
      00000000000e8000-00000000000ebfff (prio 1, ram): alias pam-rom @pc.ram 00000000000e8000-00000000000ebfff [disabled]
      00000000000e8000-00000000000ebfff (prio 1, i/o): alias pam-pci @pci 00000000000e8000-00000000000ebfff
      00000000000ec000-00000000000effff (prio 1, ram): alias pam-ram @pc.ram 00000000000ec000-00000000000effff [disabled]
      00000000000ec000-00000000000effff (prio 1, ram): alias pam-pci @pc.ram 00000000000ec000-00000000000effff [disabled]
      00000000000ec000-00000000000effff (prio 1, ram): alias pam-rom @pc.ram 00000000000ec000-00000000000effff [disabled]
      00000000000ec000-00000000000effff (prio 1, i/o): alias pam-pci @pci 00000000000ec000-00000000000effff
      00000000000f0000-00000000000fffff (prio 1, ram): alias pam-ram @pc.ram 00000000000f0000-00000000000fffff [disabled]
      00000000000f0000-00000000000fffff (prio 1, ram): alias pam-pci @pc.ram 00000000000f0000-00000000000fffff [disabled]
      00000000000f0000-00000000000fffff (prio 1, ram): alias pam-rom @pc.ram 00000000000f0000-00000000000fffff [disabled]
      00000000000f0000-00000000000fffff (prio 1, i/o): alias pam-pci @pci 00000000000f0000-00000000000fffff
      00000000fec00000-00000000fec00fff (prio 0, i/o): ioapic
      00000000fed00000-00000000fed003ff (prio 0, i/o): hpet
      00000000fee00000-00000000feefffff (prio 4096, i/o): apic-msi

After:

  (qemu) info mtree
  memory-region: system
    0000000000000000-ffffffffffffffff (prio 0, i/o): system
      0000000000000000-0000000007ffffff (prio 0, ram): alias ram-below-4g @pc.ram 0000000000000000-0000000007ffffff
      0000000000000000-ffffffffffffffff (prio -1, i/o): pci
        00000000000a0000-00000000000bffff (prio 1, i/o): vga-lowmem
        00000000000c0000-00000000000dffff (prio 1, rom): pc.rom
        00000000000e0000-00000000000fffff (prio 1, rom): alias isa-bios @pc.bios 0000000000020000-000000000003ffff
        00000000fffc0000-00000000ffffffff (prio 0, rom): pc.bios
      00000000000a0000-00000000000bffff (prio 1, i/o): alias smram-region @pci 00000000000a0000-00000000000bffff
      00000000000c0000-00000000000c3fff (prio 1, i/o): alias pam-pci @pci 00000000000c0000-00000000000c3fff
      00000000000c4000-00000000000c7fff (prio 1, i/o): alias pam-pci @pci 00000000000c4000-00000000000c7fff
      00000000000c8000-00000000000cbfff (prio 1, i/o): alias pam-pci @pci 00000000000c8000-00000000000cbfff
      00000000000cc000-00000000000cffff (prio 1, i/o): alias pam-pci @pci 00000000000cc000-00000000000cffff
      00000000000d0000-00000000000d3fff (prio 1, i/o): alias pam-pci @pci 00000000000d0000-00000000000d3fff
      00000000000d4000-00000000000d7fff (prio 1, i/o): alias pam-pci @pci 00000000000d4000-00000000000d7fff
      00000000000d8000-00000000000dbfff (prio 1, i/o): alias pam-pci @pci 00000000000d8000-00000000000dbfff
      00000000000dc000-00000000000dffff (prio 1, i/o): alias pam-pci @pci 00000000000dc000-00000000000dffff
      00000000000e0000-00000000000e3fff (prio 1, i/o): alias pam-pci @pci 00000000000e0000-00000000000e3fff
      00000000000e4000-00000000000e7fff (prio 1, i/o): alias pam-pci @pci 00000000000e4000-00000000000e7fff
      00000000000e8000-00000000000ebfff (prio 1, i/o): alias pam-pci @pci 00000000000e8000-00000000000ebfff
      00000000000ec000-00000000000effff (prio 1, i/o): alias pam-pci @pci 00000000000ec000-00000000000effff
      00000000000f0000-00000000000fffff (prio 1, i/o): alias pam-pci @pci 00000000000f0000-00000000000fffff
      00000000fec00000-00000000fec00fff (prio 0, i/o): ioapic
      00000000fed00000-00000000fed003ff (prio 0, i/o): hpet
      00000000fee00000-00000000feefffff (prio 4096, i/o): apic-msi

The old behavior is preserved using 'info mtree -D'.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>