avcodec/pthread_frame: remove unused variable

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

libavcodec/pthread_frame.c

@@ -316,7 +316,6 @@ static int submit_packet(PerThreadContext *p, AVPacket *avpkt)
     FrameThreadContext *fctx = p->parent;
     PerThreadContext *prev_thread = fctx->prev_thread;
     const AVCodec *codec = p->avctx->codec;
-    int ret;
 
     if (!avpkt->size && !(codec->capabilities & CODEC_CAP_DELAY)) return 0;