OvmfPkg: SmmCpuFeaturesLib: implement SMRAM state save map access

OvmfPkg: SmmCpuFeaturesLib: implement SMRAM state save map access

This implementation copies SMRAM state save map access from the
PiSmmCpuDxeSmm module.

The most notable change is:

- dropping support for EFI_SMM_SAVE_STATE_REGISTER_IO

- changing the implementation of EFI_SMM_SAVE_STATE_REGISTER_LMA to use
  the SMM revision id instead of a local variable (which
  UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c initializes from CPUID's LM
  bit).  This accounts for QEMU's implementation of x86_64, which always
  uses revision 0x20064 even if the LM bit is zero.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[lersek@redhat.com: reflow commit message & fix typo, convert patch to
 CRLF]

Cc: Paolo Bonzini <pbonzini@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Michael Kinney <michael.d.kinney@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19056 6f19259b-4bc3-4df7-8a09-765794883524