In gxf muxer, fix number of flt entries based on patch by Reuben Martin, reuben dot m at gmail dot com

Originally committed as revision 25399 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/gxfenc.c

@@ -365,7 +365,7 @@ static int gxf_write_flt_packet(AVFormatContext *s)
     ByteIOContext *pb = s->pb;
     int64_t pos = url_ftell(pb);
     int fields_per_flt = (gxf->nb_fields+1) / 1000 + 1;
-    int flt_entries = gxf->nb_fields / fields_per_flt - 1;
+    int flt_entries = gxf->nb_fields / fields_per_flt;
     int i = 0;
 
     gxf_write_packet_header(pb, PKT_FLT);