UefiCpuPkg/PiSmmCpuDxeSmm: Add gEfiVariableArchProtocolGuid dependency

UefiCpuPkg/PiSmmCpuDxeSmm: Add gEfiVariableArchProtocolGuid dependency

PiSmmCpuDxeSmm driver's entry point will get some PCDs supported dynamic type.
In case those PCDs are set as DynamicHii type in platform DSC File, it implies
that EFI Variable Arch protocol is required.

This fix is to add gEfiVariableArchProtocolGuid dependency on PiSmmCpuDxeSmm
driver to make sure those DynamicHii PCDs could be read correctly.

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