acpi: pci: use build_append_foo() API to construct MCFG

acpi: pci: use build_append_foo() API to construct MCFG

build_append_foo() API doesn't need explicit endianness conversions
which eliminates a source of errors and it makes build_mcfg() look like
declarative definition of MCFG table in ACPI spec, which makes it easy
to review.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Suggested-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
v3:
   * add some comment on the Configuration Space base address allocation
     structure
v2:
   * miss the reserved[8] of MCFG in last version, add it back
   * drop SOBs and make sure bios-tables-test all OK
Message-Id: <20190521062836.6541-3-richardw.yang@linux.intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>