avcodec/tdsc: return the packet size instead of 0

Most decoders return the amount of data used.
This is more consistent
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/tdsc.c

@@ -609,7 +609,7 @@ static int tdsc_decode_frame(AVCodecContext *avctx, void *data,
     }
     *got_frame = 1;
 
-    return 0;
+    return avpkt->size;
 }
 
 AVCodec ff_tdsc_decoder = {