avformat/vqf: Use 64bit for ret to avoid overflow

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit cb086871)
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/vqf.c

@@ -261,7 +261,7 @@ static int vqf_read_seek(AVFormatContext *s,
 {
     VqfContext *c = s->priv_data;
     AVStream *st;
-    int ret;
+    int64_t ret;
     int64_t pos;
 
     st = s->streams[stream_index];