net: phy: Set the driver when registering an MDIO bus device

mdiobus_register() registers a device which is already bound to a driver.
Hence, the driver pointer should be set properly in order to track down
the driver associated to the MDIO bus.

This will be used to allow ethernet driver to pin down a MDIO bus driver,
preventing it from being unloaded while the PHY device is running.
Reviewed-by: NFlorian Fainelli <f.fainelli@gmail.com>
Tested-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NEzequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/phy/mdio_bus.c

@@ -255,6 +255,7 @@ int mdiobus_register(struct mii_bus *bus)
 
 	bus->dev.parent = bus->parent;
 	bus->dev.class = &mdio_bus_class;
+	bus->dev.driver = bus->parent->driver;
 	bus->dev.groups = NULL;
 	dev_set_name(&bus->dev, "%s", bus->id);