MdeModulePkg: Add PCD PcdPteMemoryEncryptionAddressOrMask

This PCD holds the address mask for page table entries when memory
encryption is enabled on AMD processors supporting the Secure Encrypted
Virtualization (SEV) feature.

Cc: Feng Tian <feng.tian@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Leo Duran <leo.duran@amd.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>