MdeModulePkg/PiSmmCore: Replace BASE_4GB with MAX_ADDRESS check.

MdeModulePkg/PiSmmCore: Replace BASE_4GB with MAX_ADDRESS check.

PI specification Vol 4 - SMM does not have any limitation of BASE_4GB for SMM.
So we should replace BASE_4GB check with MAX_ADDRESS check to make sure
the SMM memory is accessible by SMM Core.

Cc: Jeff Fan <jeff.fan@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>