MdePkg UefiSpec.h: Update comments for OEM reserved memory type.
MdePkg UefiSpec.h: Update comments for OEM reserved memory type.

UEFI 2.5 Spec:
MemoryType values in the range 0x70000000..0x7FFFFFFF
are reserved for OEM use.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

git-svn-id: 3158a46dfd52e07d1fda3e32e1ab2e353a00b20f@17459 6f19259b-4bc3-4df7-8a09-765794883524

MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2