batman-adv: Store modification counter via hash helpers

Multiple datastructures use the hash helper functions to add and remove
entries from the simple hlist based hashes. These are often also dumped to
userspace via netlink and thus should have a generation sequence counter.

Reported-by: Matthias Schiffer <mschiffer@universe-factory.net>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
diff --git a/net/batman-adv/hash.c b/net/batman-adv/hash.c
index 7b49e40..9194f4d 100644
--- a/net/batman-adv/hash.c
+++ b/net/batman-adv/hash.c
@@ -32,6 +32,8 @@ static void batadv_hash_init(struct batadv_hashtable *hash)
 		INIT_HLIST_HEAD(&hash->table[i]);
 		spin_lock_init(&hash->list_locks[i]);
 	}
+
+	atomic_set(&hash->generation, 0);
 }
 
 /**