UefiCpuPkg: Replace Opcode with the corresponding instructions.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3790

Replace Opcode with the corresponding instructions.
The code changes have been verified with CompareBuild.py tool, which
can be used to compare the results of two different EDK II builds to
determine if they generate the same binaries.
(tool link: https://github.com/mdkinney/edk2/tree/sandbox/CompareBuild)

Signed-off-by: Jason Lou <yun.lou@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>

UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm

@@ -1,5 +1,5 @@
 ;------------------------------------------------------------------------------ ;
-; Copyright (c) 2015 - 2021, Intel Corporation. All rights reserved.<BR>
+; Copyright (c) 2015 - 2022, Intel Corporation. All rights reserved.<BR>
 ; SPDX-License-Identifier: BSD-2-Clause-Patent
 ;
 ; Module Name:
@@ -345,7 +345,7 @@ BITS 64
     ;
     ; Far return into 32-bit mode
     ;
-o64 retf
+    retfq
 
 BITS 32
 CompatMode:
@@ -507,7 +507,7 @@ NoSevEs:
     ;
     ; Far return into 32-bit mode
     ;
-o64 retf
+    retfq
 
 BITS 32
 PmEntry: