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: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 388f992..09deef4 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -431,7 +431,7 @@
 	err = phy_device_register(phydev);
 	if (err) {
 		phy_device_free(phydev);
-		return NULL;
+		return ERR_PTR(-ENODEV);
 	}
 
 	return phydev;