net: ethernet: mtk-star-emac: fix error return code in mtk_star_enable()

Fix to return a negative error code from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: 8c7bd5a454 ("net: ethernet: mtk-star-emac: new driver")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>
Acked-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Link: https://lore.kernel.org/r/1605180879-2573-1-git-send-email-zhangchangzhong@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mediatek/mtk_star_emac.c

@@ -966,6 +966,7 @@ static int mtk_star_enable(struct net_device *ndev)
 				      mtk_star_adjust_link, 0, priv->phy_intf);
 	if (!priv->phydev) {
 		netdev_err(ndev, "failed to connect to PHY\n");
+		ret = -ENODEV;
 		goto err_free_irq;
 	}