batman-adv: Convert batadv_bla_backbone_gw to kref

batman-adv uses a self-written reference implementation which is just based
on atomic_t. This is less obvious when reading the code than kref and
therefore increases the change that the reference counting will be missed.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <a@unstable.cc>
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 868f6b5..595f524 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -930,7 +930,7 @@
 	atomic_t request_sent;
 	u16 crc;
 	spinlock_t crc_lock; /* protects crc */
-	atomic_t refcount;
+	struct kref refcount;
 	struct rcu_head rcu;
 };