batman-adv: correctly set the data field in the TT_REPONSE packet

In the TT_RESPONSE packet, the number of carried entries is not correctly set.
This leads to a wrong interpretation of the packet payload on the receiver side
causing random entries to be added to the global translation table. Therefore
the latter gets always corrupted, triggering a table recovery all the time.

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>