The BaseTools/Scripts/ConvertMasmToNasm.py script was used to convert
X64/AsmFuncs.asm to X64/AsmFuncs.nasm.
And, manually add o16 prefix to specify 16bit operation.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Liming Gao <liming.gao@intel.com>