mov_read_packet: if dv_get_packet fails, return exactly its error value

instead of always -1 (makes no real difference currently since dv_get_packet
always returns -1 so far).

Originally committed as revision 19262 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/mov.c

@@ -2107,8 +2107,9 @@ static int mov_read_packet(AVFormatContext *s, AVPacket *pkt)
         dv_produce_packet(mov->dv_demux, pkt, pkt->data, pkt->size);
         av_free(pkt->data);
         pkt->size = 0;
-        if (dv_get_packet(mov->dv_demux, pkt) < 0)
-            return -1;
+        ret = dv_get_packet(mov->dv_demux, pkt);
+        if (ret < 0)
+            return ret;
     }
 #endif
     pkt->stream_index = sc->ffindex;