Add back previously removed non-existing function params in doxygen comments.

Originally committed as revision 24131 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/rl2.c

@@ -174,6 +174,8 @@ static av_cold int rl2_decode_init(AVCodecContext *avctx)
  * @param avctx decoder context
  * @param data decoded frame
  * @param data_size size of the decoded frame
+ * @param buf input buffer
+ * @param buf_size input buffer size
  * @return 0 success, -1 on error
  */
 static int rl2_decode_frame(AVCodecContext *avctx,