avidec: fix a memleak in the dv init code.

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

libavformat/avidec.c

@@ -484,6 +484,7 @@ static int avi_read_header(AVFormatContext *s)
                 ast = s->streams[0]->priv_data;
                 av_freep(&s->streams[0]->codec->extradata);
                 av_freep(&s->streams[0]->codec);
+                av_freep(&s->streams[0]->info);
                 av_freep(&s->streams[0]);
                 s->nb_streams = 0;
                 if (CONFIG_DV_DEMUXER) {