batman-adv: improved gateway tq-based selection

If a client issues a DHCPREQUEST for renewal, the packet is dropped
if the old destination (the old gateway for the client) TQ is smaller
than the current best gateway TQ less GW_THRESHOLD

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

diff --cc net/batman-adv/gateway_client.c
Simple merge

diff --cc net/batman-adv/gateway_client.h
Simple merge

diff --cc net/batman-adv/main.h
Simple merge

diff --cc net/batman-adv/soft-interface.c
Simple merge