BaseTools/GenFfs: add FFS file types for MM modules.

BaseTools/GenFfs: add FFS file types for MM modules.

PI specification v1.5 defines new firmware volume file types
for Management Mode (MM).

This patch adds the new file type EFI_FV_FILETYPE_MM_STANDALONE and
EFI_FV_FILETYPE_MM_CORE_STANDALONE in GenFfs tool.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Supreeth Venkatesh <supreeth.venkatesh@arm.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>