can: j1939: j1939_sk_queue_activate_next_locked(): replace WARN_ON_ONCE with netdev_warn_once()

We should warn user-space that it is doing something wrong when trying
to activate sessions with identical parameters but WARN_ON_ONCE macro
can not be used here as it serves a different purpose.

So it would be good to replace it with netdev_warn_once() message.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: 9d71dd0c ("can: add support of SAE J1939 protocol")
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/all/20220729143655.1108297-1-pchelkin@ispras.ru
[mkl: fix indention]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

net/can/j1939/socket.c

@@ -178,7 +178,10 @@ static void j1939_sk_queue_activate_next_locked(struct j1939_session *session)
 	if (!first)
 		return;
 
-	if (WARN_ON_ONCE(j1939_session_activate(first))) {
+	if (j1939_session_activate(first)) {
+		netdev_warn_once(first->priv->ndev,
+				 "%s: 0x%p: Identical session is already activated.\n",
+				 __func__, first);
 		first->err = -EBUSY;
 		goto activate_next;
 	} else {