mxfdec: fix return variable type for avio_seek

Signed-off-by: Marton Balint <cus@passwd.hu>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/mxfdec.c

@@ -2441,6 +2441,7 @@ static int mxf_read_seek(AVFormatContext *s, int stream_index, int64_t sample_ti
     MXFContext* mxf = s->priv_data;
     int64_t seekpos;
     int i, ret;
+    int64_t ret64;
     MXFIndexTable *t;
     MXFTrack *source_track = st->priv_data;
 
@@ -2455,8 +2456,8 @@ static int mxf_read_seek(AVFormatContext *s, int stream_index, int64_t sample_ti
         sample_time = 0;
     seconds = av_rescale(sample_time, st->time_base.num, st->time_base.den);
 
-    if ((ret = avio_seek(s->pb, (s->bit_rate * seconds) >> 3, SEEK_SET)) < 0)
-        return ret;
+    if ((ret64 = avio_seek(s->pb, (s->bit_rate * seconds) >> 3, SEEK_SET)) < 0)
+        return ret64;
     ff_update_cur_dts(s, st, sample_time);
     mxf->current_edit_unit = sample_time;
     } else {