MdePkg: Add header file for Firmware Interface Table specification.

MdePkg: Add header file for Firmware Interface Table specification.

This patch add FirmwareInterfaceTable.h for the Firmware Interface Table
BIOS specification.

This is to remove future edk2 dependency on edk2-platforms repo. The file
content comes from
 edk2-platforms\Silicon\Intel\IntelSiliconPkg\Include\IndustryStandard

link: https://tianocore.acgmultimedia.com/show_bug.cgi?id=2449
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Siyuan Fu <siyuan.fu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>