mdio_bus: don't return NULL from mdiobus_scan()

I've finally noticed that mdiobus_scan() also returns either NULL or error
value on failure.  Return ERR_PTR(-ENODEV) instead of NULL since this is
the  error value  already filtered out by the callers that want to ignore
the  MDIO address scan failure...
Signed-off-by: NSergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/phy/mdio_bus.c

@@ -431,7 +431,7 @@ struct phy_device *mdiobus_scan(struct mii_bus *bus, int addr)
 	err = phy_device_register(phydev);
 	if (err) {
 		phy_device_free(phydev);
-		return NULL;
+		return ERR_PTR(-ENODEV);
 	}
 
 	return phydev;