SecurityPkg: Replace UnicodeStrToAsciiStr/AsciiStrToUnicodeStr

SecurityPkg: Replace UnicodeStrToAsciiStr/AsciiStrToUnicodeStr

It is the follow up of 3ab41b7a325ca11a12b42f5ad1661c4b6791cb49
to replace UnicodeStrToAsciiStr/AsciiStrToUnicodeStr with
UnicodeStrToAsciiStrS/AsciiStrToUnicodeStrS.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Chao Zhang <chao.b.zhang@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
Reviewed-by: Chao Zhang <chao.b.zhang@intel.com>