UefiCpuPkg/PiSmmCpuDxeSmm: Fix SMM stack offset is not correct

UefiCpuPkg/PiSmmCpuDxeSmm: Fix SMM stack offset is not correct

In function InitGdt(), SmiPFHandler() and Gen4GPageTable(), it uses
 CpuIndex * mSmmStackSize to get the SMM stack address offset for
 multi processor. It misses the SMM Shadow Stack Size. Each processor
 will use mSmmStackSize + mSmmShadowStackSize in the memory.
It should use CpuIndex * (mSmmStackSize + mSmmShadowStackSize) to get
 this SMM stack address offset. If mSmmShadowStackSize > 0 and multi
 processor enabled, it will get the wrong offset value.
CET shadow stack feature will set the value of mSmmShadowStackSize.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3237

Signed-off-by: Sheng Wei <w.sheng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Roger Feng <roger.feng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>