UefiCpuPkg/PiSmmCpuDxeSmm: use mnemonics for FXSAVE(64)/FXRSTOR(64)

NASM introduced FXSAVE / FXRSTOR support in commit 900fa5b26b8f ("NASM
0.98p3-hpa", 2002-04-30), which commit stands for the nasm-0.98p3-hpa
release.

NASM introduced FXSAVE64 / FXRSTOR64 support in commit 3a014348ca15
("insns: add FXSAVE64/FXRSTOR64, drop np prefix", 2010-07-07), which was
part of the "nasm-2.09" release.

Edk2 requires nasm-2.10 or later for use with the GCC toolchain family,
and nasm-2.12.01 or later for use with all other toolchain families.
Replace the binary encoding of the FXSAVE(64)/FXRSTOR(64) instructions
with mnemonics.

I verified that the "Ia32/SmiException.obj", "X64/SmiEntry.obj" and
"X64/SmiException.obj" files are rebuilt after this patch, without any
change in content.

This patch removes the last instructions encoded with DBs from
PiSmmCpuDxeSmm.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=866
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm

@@ -182,8 +182,7 @@ _SmiHandler:
     ; Save FP registers
     ;
     sub     rsp, 0x200
-    DB      0x48                         ; FXSAVE64
-    fxsave  [rsp]
+    fxsave64 [rsp]
 
     add     rsp, -0x20
 
@@ -201,8 +200,7 @@ _SmiHandler:
     ;
     ; Restore FP registers
     ;
-    DB      0x48                         ; FXRSTOR64
-    fxrstor [rsp]
+    fxrstor64 [rsp]
 
     add     rsp, 0x200