failover: Fix error return code in net_failover_create

if failover_register failed, 'err' code should be set correctly

Fixes: cfc80d9a1163 ("net: Introduce net_failover driver")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/net_failover.c

@@ -764,8 +764,10 @@ struct failover *net_failover_create(struct net_device *standby_dev)
 	netif_carrier_off(failover_dev);
 
 	failover = failover_register(failover_dev, &net_failover_ops);
-	if (IS_ERR(failover))
+	if (IS_ERR(failover)) {
+		err = PTR_ERR(failover);
 		goto err_failover_register;
+	}
 
 	return failover;