northbridge/amd/agesa/family16kb: Add MMCONF res to PCI_DOMAIN

This is a port of the following:
commit d5c998be99709c92f200b3b08aed2ca3fee2d519

  The coreboot resource allocator doesn't respect resources
  claimed in the APIC_CLUSTER. Move the MMCONF resource to the
  PCI_DOMAIN to prevent overlap with PCI devices.

Change-Id: I49167dd3f15d0203a7db8950880ab03171d5c170
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/7533
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>