mpeg4: report frame decoding completion at ff_MPV_frame_end().

Prevents hangs on corrupt input.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org

libavcodec/mpegvideo.c

@@ -1409,8 +1409,7 @@ void ff_MPV_frame_end(MpegEncContext *s)
     s->avctx->coded_frame = &s->current_picture_ptr->f;
 
     if (s->codec_id != CODEC_ID_H264 && s->current_picture.f.reference) {
-        ff_thread_report_progress(&s->current_picture_ptr->f,
-                                  s->mb_height - 1, 0);
+        ff_thread_report_progress(&s->current_picture_ptr->f, INT_MAX, 0);
     }
 }