avcodec/rscc: 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/rscc.c

@@ -324,6 +324,7 @@ static int rscc_decode_frame(AVCodecContext *avctx, void *data,
     }
     *got_frame = 1;
 
+    ret = avpkt->size;
 end:
     av_free(inflated_tiles);
     return ret;