MdePkg: 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>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Zhiguang Liu <zhiguang.liu@intel.com>

MdePkg/Library/BaseLib/Ia32/ReadDr5.nasm

@@ -1,6 +1,6 @@
 ;------------------------------------------------------------------------------
 ;
-; Copyright (c) 2006, Intel Corporation. All rights reserved.<BR>
+; Copyright (c) 2006 - 2022, Intel Corporation. All rights reserved.<BR>
 ; SPDX-License-Identifier: BSD-2-Clause-Patent
 ;
 ; Module Name:
@@ -31,8 +31,8 @@ ASM_PFX(AsmReadDr5):
     ; this register will cause a #UD exception.
     ;
     ; MS assembler doesn't support this instruction since no one would use it
-    ; under normal circustances. Here opcode is used.
+    ; under normal circustances.
     ;
-    DB      0xf, 0x21, 0xe8
+    mov     eax, dr5
     ret