MdeModulePkg/Udf: Refine function description comments

MdeModulePkg/Udf: Refine function description comments

Cc: Paulo Alcantara <pcacjr@zytor.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Dandan Bi <dandan.bi@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Paulo Alcantara <pcacjr@zytor.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>