net: mdio: mvusb: Fix an error handling path in mvusb_mdio_probe()

Should of_mdiobus_register() fail, a previous usb_get_dev() call should be
undone as in the .disconnect function.

Fixes: 04e37d92 ("net: phy: add marvell usb to mdio controller")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/mdio/mdio-mvusb.c

@@ -67,6 +67,7 @@ static int mvusb_mdio_probe(struct usb_interface *interface,
 	struct device *dev = &interface->dev;
 	struct mvusb_mdio *mvusb;
 	struct mii_bus *mdio;
+	int ret;
 
 	mdio = devm_mdiobus_alloc_size(dev, sizeof(*mvusb));
 	if (!mdio)
@@ -87,7 +88,15 @@ static int mvusb_mdio_probe(struct usb_interface *interface,
 	mdio->write = mvusb_mdio_write;
 
 	usb_set_intfdata(interface, mvusb);
-	return of_mdiobus_register(mdio, dev->of_node);
+	ret = of_mdiobus_register(mdio, dev->of_node);
+	if (ret)
+		goto put_dev;
+
+	return 0;
+
+put_dev:
+	usb_put_dev(mvusb->udev);
+	return ret;
 }
 
 static void mvusb_mdio_disconnect(struct usb_interface *interface)