MdeModulePkg PiSmmCore: Remove unreferenced symbol for SMRAM profile
MdeModulePkg PiSmmCore: Remove unreferenced symbol for SMRAM profile

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=370

Use GLOBAL_REMOVE_IF_UNREFERENCED for some SMRAM profile global variables,
then their symbols could be removed when SMRAM profile is disabled.

Cc: Jiewen Yao <364a90bfebd1f362ebb7b48e4bf8ec010adef203@intel.com>
Cc: Feng Tian <e66bb7e9f36c82a029035c5885acf75500d07e68@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <5c6bb72efe464613af94e84c05522a361b23844a@intel.com>
Reviewed-by: Jiewen Yao <364a90bfebd1f362ebb7b48e4bf8ec010adef203@intel.com>

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