MdePkg: Remove the macro definitions regarding Opcode.

MdePkg: Remove the macro definitions regarding Opcode.

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

Remove the macro definitions regarding Opcode because new version of
NASM tool(e.g. v2.15.05) supports the corresponding instructions.
Note: This patch need to be merged after other NASM code change to avoid
compilation errors.

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>