This commit refines the logic for AsciiStrnLenS and StrnLenS. It makes the logic more straightforward to prevent possible mis-reports by static code checkers. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Hao Wu <hao.a.wu@intel.com> Reviewed-by: Liming Gao <liming.gao@intel.com>