Similar to the SMBus io registers there is a power management io range
that is set via similar base address reg and enable bit. Some handling
of this was already there but with several problems: using the wrong
registers and bits, wrong size range, not acually updating mapping and
handling reset correctly, nor emulating any of the actual io
registers. Some of these errors are fixed up here.

After this patch we use the correct base address register, enable bit
and region size and allow guests to map/unmap this region, but we
still don't emulate any of the registers in this range.

PMD notes regarding the Configuration Space Power Management Registers:

  - 0x40 General Configuration 0

  - 0x41 General Configuration 1

    . Bit 7: I/O Enable for ACPI I/O Base

  - 0x48 Power Mgmt I/O Base

    . Bit 0: Always set
    . Bits 7-15: Power Management I/O Register Base Address
      (this explains the change 0xffc0 -> 0xff80)

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Message-Id: <cff9b2442d3e2e1cfbdcbc2dfbb559031b4b1cc1.1610223397.git.balaton@eik.bme.hu>
[PMD: Split original patch, this is part 4/4, added notes]
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>