batman,rcu: convert call_rcu(neigh_node_free_rcu) to kfree()

The RCU callback neigh_node_free_rcu() just calls kfree(), so we can use
kfree_rcu() instead of call_rcu().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Marek Lindner <lindner_marek@yahoo.de>
Cc: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Acked-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Sven Eckelmann <sven@narfation.org>

net/batman-adv/originator.c

@@ -56,18 +56,10 @@ int originator_init(struct bat_priv *bat_priv)
 	return 0;
 }
 
-static void neigh_node_free_rcu(struct rcu_head *rcu)
-{
-	struct neigh_node *neigh_node;
-
-	neigh_node = container_of(rcu, struct neigh_node, rcu);
-	kfree(neigh_node);
-}
-
 void neigh_node_free_ref(struct neigh_node *neigh_node)
 {
 	if (atomic_dec_and_test(&neigh_node->refcount))
-		call_rcu(&neigh_node->rcu, neigh_node_free_rcu);
+		kfree_rcu(neigh_node, rcu);
 }
 
 struct neigh_node *create_neighbor(struct orig_node *orig_node,