pc: Eliminate PcPciInfo

PcPciInfo has two (ill-named) members: Range w32 is the PCI hole, and
w64 is the PCI64 hole.

Three users:

* I440FXState and MCHPCIState have a member PcPciInfo pci_info, but
  only pci_info.w32 is actually used.  This is confusing.  Replace by
  Range pci_hole.

* acpi_build() uses auto PcPciInfo pci_info to forward both PCI holes
  from acpi_get_pci_info() to build_dsdt().  Replace by two variables
  Range pci_hole, pci_hole64.  Rename acpi_get_pci_info() to
  acpi_get_pci_holes().

PcPciInfo is now unused; drop it.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>