UefiCpuPkg/PiSmmCpuDxeSmm: Add paging protection.

PiSmmCpuDxeSmm consumes SmmAttributesTable and setup page table:
1) Code region is marked as read-only and Data region is non-executable,
if the PE image is 4K aligned.
2) Important data structure is set to RO, such as GDT/IDT.
3) SmmSaveState is set to non-executable,
and SmmEntrypoint is set to read-only.
4) If static page is supported, page table is read-only.

We use page table to protect other components, and itself.

If we use dynamic paging, we can still provide *partial* protection.
And hope page table is not modified by other components.

The XD enabling code is moved to SmiEntry to let NX take effect.

Cc: Jeff Fan <jeff.fan@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Cc: Star Zeng <star.zeng@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>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>

UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmProfileArch.c

@@ -1,7 +1,7 @@
 /** @file
 IA-32 processor specific functions to enable SMM profile.
 
-Copyright (c) 2012 - 2015, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2012 - 2016, Intel Corporation. All rights reserved.<BR>
 This program and the accompanying materials
 are licensed and made available under the terms and conditions of the BSD License
 which accompanies this distribution.  The full text of the license may be found at
@@ -24,7 +24,7 @@ InitSmmS3Cr3 (
   VOID
   )
 {
-  mSmmS3ResumeState->SmmS3Cr3 = Gen4GPageTable (0, TRUE);
+  mSmmS3ResumeState->SmmS3Cr3 = Gen4GPageTable (TRUE);
 
   return ;
 }