drivers/of/of_mdio.c:fix of_mdiobus_register()

When registers a phy_device successful, should terminate the loop
or the phy_device would be registered in other addr. If there are
multiple PHYs without reg properties, it will go wrong.

Signed-off-by: Dajun Jin <adajunjin@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>