xfrm: fix rcu_read_unlock usage in xfrm_local_error

In the xfrm_local_error, rcu_read_unlock should be called when afinfo
is not NULL. because xfrm_state_get_afinfo calls rcu_read_unlock
if afinfo is NULL.

Fixes: af5d27c4e1 ("xfrm: remove xfrm_state_put_afinfo")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/xfrm/xfrm_output.c

@@ -285,8 +285,9 @@ void xfrm_local_error(struct sk_buff *skb, int mtu)
 		return;
 
 	afinfo = xfrm_state_get_afinfo(proto);
-	if (afinfo)
+	if (afinfo) {
 		afinfo->local_error(skb, mtu);
-	rcu_read_unlock();
+		rcu_read_unlock();
+	}
 }
 EXPORT_SYMBOL_GPL(xfrm_local_error);