UefiCpuPkg PiSmmCpuDxeSmm: Fixed #double fault on #page fault for IA32

When StackGuard is enabled on IA32, the #double fault exception
is reported instead of #page fault.

This issue does not exist on X64, or IA32 without StackGuard.

The fix at e4435f710c was incomplete.

It is because AllocateCodePages() is used to allocate buffer for
GDT and TSS, the code pages will be set to RO in SetMemMapAttributes().
But IA32 Stack Guard need use task switch to switch stack that need
write GDT and TSS, so AllocateCodePages() could not be used.

This patch uses AllocatePages() instead of AllocateCodePages() to
allocate buffer for GDT and TSS if StackGuard is enabled on IA32.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>

UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h

@@ -1,7 +1,7 @@
 /** @file
 Agent Module to load other modules to deploy SMM Entry Vector for X86 CPU.
 
-Copyright (c) 2009 - 2017, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2009 - 2018, Intel Corporation. All rights reserved.<BR>
 Copyright (c) 2017, AMD Incorporated. All rights reserved.<BR>
 
 This program and the accompanying materials
@@ -509,14 +509,6 @@ InitGdt (
   OUT UINTN  *GdtStepSize
   );
 
-/**
-  This function sets GDT/IDT buffer to be RO and XP.
-**/
-VOID
-PatchGdtIdtMap (
-  VOID
-  );
-
 /**
 
   Register the SMM Foundation entry point.