UefiCpuPkg: Move MigrateGdt from DiscoverMemory to TempRamDone. (CVE-2019-11098)

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1614
REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3160

The GDT still in flash with commit 60b12e69fb
after TempRamDone

So move the action to TempRamDone event to avoid reading GDT from flash.

Signed-off-by: Guomin Jiang <guomin.jiang@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Debkumar De <debkumar.de@intel.com>
Cc: Harry Han <harry.han@intel.com>
Cc: Catharine West <catharine.west@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>

UefiCpuPkg/CpuMpPei/CpuPaging.c

@@ -605,17 +605,9 @@ MemoryDiscoveredPpiNotifyCallback (
 {
   EFI_STATUS              Status;
   BOOLEAN                 InitStackGuard;
-  BOOLEAN                 InterruptState;
   EDKII_MIGRATED_FV_INFO  *MigratedFvInfo;
   EFI_PEI_HOB_POINTERS    Hob;
 
-  if (PcdGetBool (PcdMigrateTemporaryRamFirmwareVolumes)) {
-    InterruptState = SaveAndDisableInterrupts ();
-    Status = MigrateGdt ();
-    ASSERT_EFI_ERROR (Status);
-    SetInterruptState (InterruptState);
-  }
-
   //
   // Paging must be setup first. Otherwise the exception TSS setup during MP
   // initialization later will not contain paging information and then fail