Currently, mCpuSmmRestrictedMemoryAccess is only used by the
IsRestrictedMemoryAccess(). And IsRestrictedMemoryAccess() can
consume the PcdCpuSmmRestrictedMemoryAccess directly. Therefore,
mCpuSmmRestrictedMemoryAccess can be cleaned to simply the code
logic.
Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>