UefiCpuPkg/PiSmmCpuDxeSmm: Remove MTRRs from PSD structure

UefiCpuPkg/PiSmmCpuDxeSmm: Remove MTRRs from PSD structure

https://bugzilla.tianocore.org/show_bug.cgi?id=277

All CPUs use the same MTRR settings.  Move MTRR settings
from a field in the PROCESSOR_SMM_DESCRIPTOR structure into
a module global variable.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jeff Fan <jeff.fan@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael Kinney <michael.d.kinney@intel.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Feng Tian <feng.tian@intel.com>