net,rcu: convert call_rcu(prl_entry_destroy_rcu) to kfree

The RCU callback prl_entry_destroy_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: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: "Pekka Savola (ipv6)" <pekkas@netcore.fi>
Cc: James Morris <jmorris@namei.org>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: Patrick McHardy <kaber@trash.net>
Acked-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

net/ipv6/sit.c

@@ -401,11 +401,6 @@ ipip6_tunnel_add_prl(struct ip_tunnel *t, struct ip_tunnel_prl *a, int chg)
 	return err;
 }
 
-static void prl_entry_destroy_rcu(struct rcu_head *head)
-{
-	kfree(container_of(head, struct ip_tunnel_prl_entry, rcu_head));
-}
-
 static void prl_list_destroy_rcu(struct rcu_head *head)
 {
 	struct ip_tunnel_prl_entry *p, *n;
@@ -433,7 +428,7 @@ ipip6_tunnel_del_prl(struct ip_tunnel *t, struct ip_tunnel_prl *a)
 		     p = &x->next) {
 			if (x->addr == a->addr) {
 				*p = x->next;
-				call_rcu(&x->rcu_head, prl_entry_destroy_rcu);
+				kfree_rcu(x, rcu_head);
 				t->prl_count--;
 				goto out;
 			}