net: mdio-gpio: warn about missing bus alias id

Use a sane default bus id (rather than -ENODEV) and print a warning when
the bus alias id is missing.
Signed-off-by: NJohan Hovold <jhovold@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/phy/mdio-gpio.c

@@ -215,6 +215,10 @@ static int mdio_gpio_probe(struct platform_device *pdev)
 	if (pdev->dev.of_node) {
 		pdata = mdio_gpio_of_get_data(pdev);
 		bus_id = of_alias_get_id(pdev->dev.of_node, "mdio-gpio");
+		if (bus_id < 0) {
+			dev_warn(&pdev->dev, "failed to get alias id\n");
+			bus_id = 0;
+		}
 	} else {
 		pdata = dev_get_platdata(&pdev->dev);
 		bus_id = pdev->id;