ffmpeg: frame droping due to fps should not be a warning

This reverts part of 41e7e46cac

See: http://thread.gmane.org/gmane.comp.video.ffmpeg.user/51229
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

ffmpeg.c

@@ -895,7 +895,7 @@ static void do_video_out(AVFormatContext *s,
     nb_frames = FFMIN(nb_frames, ost->max_frames - ost->frame_number);
     if (nb_frames == 0) {
         nb_frames_drop++;
-        av_log(NULL, AV_LOG_WARNING,
+        av_log(NULL, AV_LOG_VERBOSE,
                "*** dropping frame %d from stream %d at ts %"PRId64"\n",
                ost->frame_number, ost->st->index, in_picture->pts);
         return;