After the 9f29fbd3, full mapping SMM page table is always created
regardless the value of the PcdCpuSmmRestrictedMemoryAccess. If so,
SMM PageTable Attributes can be set to ready-only since there is no
need to update it. So, this patch is to remove restricted memory
access check when setting the SMM PageTable attributes.
Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>