tty: return av_get_packet() error codes instead of converting them to EIO

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

libavformat/tty.c

@@ -135,8 +135,8 @@ static int read_packet(AVFormatContext *avctx, AVPacket *pkt)
     }
 
     pkt->size = av_get_packet(avctx->pb, pkt, n);
-    if (pkt->size <= 0)
-        return AVERROR(EIO);
+    if (pkt->size < 0)
+        return pkt->size;
     pkt->flags |= AV_PKT_FLAG_KEY;
     return 0;
 }