UefiCpuPkg: Update AddressEncMask in CpuPageTable

UefiCpuPkg: Update AddressEncMask in CpuPageTable

RFC: https://bugzilla.tianocore.org/show_bug.cgi?id=3429

MMIO region in Tdx guest is set with PcdTdxSharedBitMask in TdxDxe's
entry point. In SEV guest the page table entries is set with
PcdPteMemoryEncryptionAddressOrMask when creating 1:1 identity table.

So the AddressEncMask in GetPageTableEntry (@CpuPageTable.c) is either
PcdPteMemoryEncryptionAddressOrMask (in SEV guest), or
PcdTdxSharedBitMask (in TDX guest), or all-0 (in Legacy guest).

Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>