movenc: Add tfra entries for all tracks in a moof

Previously only tfra entries were added for the first track in each moof.

The frag_info array used for tfra can also be used for writing
other kinds of fragment indexes, where it's more important to
include all tracks.

When the separate_moof option is enabled (as in ismv), we write
a separate moof for each track, so this doesn't make any difference
in that case.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/movenc.c

@@ -2600,10 +2600,6 @@ static int mov_add_tfra_entries(AVIOContext *pb, MOVMuxContext *mov, int tracks)
                          track->cluster[0].dts;
         info->tfrf_offset = 0;
         mov_write_tfrf_tags(pb, mov, track);
-        // If writing all tracks, we currently only add a tfra entry for
-        // the first track (that actually has data to be written).
-        if (tracks < 0)
-            break;
     }
     return 0;
 }