net,rcu: convert call_rcu(in6_dev_finish_destroy_rcu) to kfree_rcu()

The rcu callback in6_dev_finish_destroy_rcu() just calls a kfree(),
so we use kfree_rcu() instead of the call_rcu(in6_dev_finish_destroy_rcu).
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

net/ipv6/addrconf.c

@@ -317,12 +317,6 @@ static void snmp6_free_dev(struct inet6_dev *idev)
 
 /* Nobody refers to this device, we may destroy it. */
 
-static void in6_dev_finish_destroy_rcu(struct rcu_head *head)
-{
-	struct inet6_dev *idev = container_of(head, struct inet6_dev, rcu);
-	kfree(idev);
-}
-
 void in6_dev_finish_destroy(struct inet6_dev *idev)
 {
 	struct net_device *dev = idev->dev;
@@ -339,7 +333,7 @@ void in6_dev_finish_destroy(struct inet6_dev *idev)
 		return;
 	}
 	snmp6_free_dev(idev);
-	call_rcu(&idev->rcu, in6_dev_finish_destroy_rcu);
+	kfree_rcu(idev, rcu);
 }
 
 EXPORT_SYMBOL(in6_dev_finish_destroy);