Update the return status description and use OUT identifier instead of IN for Digest parameter, no functionality change. Cc: Chao B Zhang <chao.b.zhang@intel.com> Cc: Jiewen Yao <jiewen.yao@intel.com> Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Star Zeng <star.zeng@intel.com> Reviewed-by: Jiewen Yao <jiewen.yao@intel.com> Reviewed-by: Chao Zhang <chao.b.zhang@intel.com>