UefiCpuPkg: Use FINIT instead of hex values

https://bugzilla.tianocore.org/show_bug.cgi?id=560

Update X64 NASM file to match IA32 NASM file
and use FINIT instruction instead of hand
assembled hex values for the FINIT instruction.

Cc: Jeff Fan <jeff.fan@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>
(cherry picked from commit b9dbc03e5a)

UefiCpuPkg/Library/BaseUefiCpuLib/X64/InitializeFpu.nasm

@@ -41,10 +41,7 @@ ASM_PFX(InitializeFloatingPointUnits):
     ;
     ; Initialize floating point units
     ;
-    ; The following opcodes stand for instruction 'finit'
-    ; to be supported by some 64-bit assemblers
-    ;
-    DB      0x9B, 0xDB, 0xE3
+    finit
     fldcw   [mFpuControlWord]
 
     ;