rcu: Use hlist_nulls_next_rcu() in hlist_nulls_add_tail_rcu()

In commit 8dbd76e7 ("tcp/dccp: fix possible race
__inet_lookup_established()"), function hlist_nulls_add_tail_rcu() was
added back, but the local variable *last* is of type hlist_nulls_node,
so use hlist_nulls_next_rcu() instead of hlist_next_rcu().
Signed-off-by: Zhao Mengmeng <zhaomengmeng@kylinos.cn>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

include/linux/rculist_nulls.h

@@ -139,7 +139,7 @@ static inline void hlist_nulls_add_tail_rcu(struct hlist_nulls_node *n,
 	if (last) {
 		n->next = last->next;
 		n->pprev = &last->next;
-		rcu_assign_pointer(hlist_next_rcu(last), n);
+		rcu_assign_pointer(hlist_nulls_next_rcu(last), n);
 	} else {
 		hlist_nulls_add_head_rcu(n, h);
 	}