UefiCpuPkg: Simplify InitializeSeparateExceptionStacks

Hide the Exception implementation details in CpuExcetionHandlerLib and
caller only need to provide buffer

Cc: Eric Dong <eric.dong@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Leif Lindholm <quic_llindhol@quicinc.com>
Cc: Dandan Bi <dandan.bi@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>
Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>

MdeModulePkg/Core/Dxe/DxeMain/DxeMain.c

@@ -1,7 +1,7 @@
 /** @file
   DXE Core Main Entry Point
 
-Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2006 - 2022, Intel Corporation. All rights reserved.<BR>
 SPDX-License-Identifier: BSD-2-Clause-Patent
 
 **/
@@ -260,7 +260,7 @@ DxeMain (
   // Setup Stack Guard
   //
   if (PcdGetBool (PcdCpuStackGuard)) {
-    Status = InitializeSeparateExceptionStacks (NULL);
+    Status = InitializeSeparateExceptionStacks (NULL, NULL);
     ASSERT_EFI_ERROR (Status);
   }