avformat: Remove unnecessary av_packet_unref()

Since bae8844e the packet will always be unreferenced when a demuxer
returns an error, so that a lot of calls to av_packet_unref() in lots of
demuxers are now redundant and can be removed.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: Marton Balint <cus@passwd.hu>

libavformat/redspark.c

@@ -140,7 +140,6 @@ static int redspark_read_packet(AVFormatContext *s, AVPacket *pkt)
 
     ret = av_get_packet(s->pb, pkt, size);
     if (ret != size) {
-        av_packet_unref(pkt);
         return AVERROR(EIO);
     }