avcodec/twinvq: return the actual number of consumed bytes

Fixes Ticket2980
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/twinvq.c

@@ -512,7 +512,7 @@ int ff_twinvq_decode_frame(AVCodecContext *avctx, void *data,
 
     *got_frame_ptr = 1;
 
-    return avctx->block_align;
+    return ret;
 }
 
 /**