can: j1939: j1939_local_ecu_get(): undo increment when j1939_local_ecu_get() fails

Since j1939_sk_bind() and j1939_sk_release() call j1939_local_ecu_put()
when J1939_SOCK_BOUND was already set, but the error handling path for
j1939_sk_bind() will not set J1939_SOCK_BOUND when j1939_local_ecu_get()
fails, j1939_local_ecu_get() needs to undo priv->ents[sa].nusers++ when
j1939_local_ecu_get() returns an error.

Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
Signed-off-by: Tetsuo Handa <[e-mail]>
Tested-by: Oleksij Rempel <[e-mail]>
Acked-by: Oleksij Rempel <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Marc Kleine-Budde <[e-mail]>

net/can/j1939/bus.c

···
 	if (!ecu)
 		ecu = j1939_ecu_create_locked(priv, name);
 	err = PTR_ERR_OR_ZERO(ecu);
-	if (err)
+	if (err) {
+		if (j1939_address_is_unicast(sa))
+			priv->ents[sa].nusers--;
 		goto done;
+	}
 
 	ecu->nusers++;
 	/* TODO: do we care if ecu->addr != sa? */