batman-adv: remove unused BATADV_BONDING_TQ_THRESHOLD constant

BATADV_BONDING_TQ_THRESHOLD is not used anymore since the implementation
of the bat_neigh_is_similar_or_better() API function.
Such function uses the more generic BATADV_TQ_SIMILARITY_THRESHOLD
constant.

Therefore, remove definition of the unused BATADV_BONDING_TQ_THRESHOLD
constant.

Signed-off-by: Antonio Quartulli <a@unstable.cc>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>