UefiCpuPkg/PiSmmCpuDxeSmm: Add MemoryMapped in SetProcessorRegister()

UefiCpuPkg/PiSmmCpuDxeSmm: Add MemoryMapped in SetProcessorRegister()

REGISTER_TYPE in UefiCpuPkg/Include/AcpiCpuData.h defines a MemoryMapped
enum value.  However support for the MemoryMapped enum is missing from
the implementation of SetProcessorRegister().  This patch adds support
for MemoryMapped type SetProcessorRegister().

One spin lock is added to avoid potential conflict when multiple processor
update the same memory space.

Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Feng Tian <feng.tian@intel.com>
Reviewed-by: Michael Kinney <michael.d.kinney@intel.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>