hw/acpi: Consolidate build_mcfg to pci.c

Now we have two identical build_mcfg functions.

Consolidate them in acpi/pci.c.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>

v4:
  * ACPI_PCI depends on both ACPI and PCI
  * rebase on latest master, adjust arm Kconfig
v3:
  * adjust changelog based on Igor's suggestion
Message-Id: <20190521062836.6541-2-richardw.yang@linux.intel.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>