net: mdio: of_mdiobus_register(): fall back to mdiobus_register() for !CONFIG_OF

If CONFIG_OF is not set, make of_mdiobus_register() call
mdiobus_register() instead of returning -ENOSYS.

This way, we can just call of_mdiobus_register() from all DT-enabled
drivers to handle the compat cases.
Signed-off-by: Daniel Mack <zonque@gmail.com>
Suggested-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Mugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/of_mdio.h

@@ -31,7 +31,12 @@ extern struct mii_bus *of_mdio_find_bus(struct device_node *mdio_np);
 #else /* CONFIG_OF */
 static inline int of_mdiobus_register(struct mii_bus *mdio, struct device_node *np)
 {
-	return -ENOSYS;
+	/*
+	 * Fall back to the non-DT function to register a bus.
+	 * This way, we don't have to keep compat bits around in drivers.
+	 */
+
+	return mdiobus_register(mdio);
 }
 
 static inline struct phy_device *of_phy_find_device(struct device_node *phy_np)