UefiCpuPkg/PiSmmCpuDxeSmm: Remove mInternalCr3 in PiSmmCpuDxeSmm

UefiCpuPkg/PiSmmCpuDxeSmm: Remove mInternalCr3 in PiSmmCpuDxeSmm

This patch is code refactoring and doesn't change any functionality.
Remove mInternalCr3 in PiSmmCpuDxe pagetable related code. In previous
code, mInternalCr3 is used to pass address of page table which is
different from Cr3 register in different level of SetMemoryAttributes
function. Now remove it and pass the page table base address from the
root function parameter to simplify the code logic.

Signed-off-by: Dun Tan <dun.tan@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>