batman-adv: don't bother flipping ->tt_data

just keep it net-endian all along

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[lindner_marek@yahoo.de: fix checkpatch warnings]
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>