Update BGRT image buffer to be stored in EfiBootSerivesData according to ACPI5.0 spec

Signed-off-by: Chao Zhang <chao.b.zhang@intel.com>
Reviewed-by: Yao Jiewen <jiewen.yao@intel.com>

git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/MdeModulePkg@14659 6f19259b-4bc3-4df7-8a09-765794883524