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

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 0f55bc29d4)

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

libavformat/omadec.c

@@ -464,7 +464,7 @@ static int oma_read_seek(struct AVFormatContext *s,
                          int stream_index, int64_t timestamp, int flags)
 {
     OMAContext *oc = s->priv_data;
-    int err = ff_pcm_read_seek(s, stream_index, timestamp, flags);
+    int64_t err = ff_pcm_read_seek(s, stream_index, timestamp, flags);
 
     if (!oc->encrypted)
         return err;