of_mdio: Enable fixed PHY support if driver is a module

The fixed_phy driver doesn't have to be built-in, and it's
important that of_mdio supports it even if it's a module.

Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/of/of_mdio.c

@@ -361,7 +361,7 @@ struct phy_device *of_phy_attach(struct net_device *dev,
 }
 EXPORT_SYMBOL(of_phy_attach);
 
-#if defined(CONFIG_FIXED_PHY)
+#if IS_ENABLED(CONFIG_FIXED_PHY)
 /*
  * of_phy_is_fixed_link() and of_phy_register_fixed_link() must
  * support two DT bindings:

include/linux/of_mdio.h

@@ -69,7 +69,7 @@ static inline int of_mdio_parse_addr(struct device *dev,
 }
 #endif /* CONFIG_OF */
 
-#if defined(CONFIG_OF) && defined(CONFIG_FIXED_PHY)
+#if defined(CONFIG_OF) && IS_ENABLED(CONFIG_FIXED_PHY)
 extern int of_phy_register_fixed_link(struct device_node *np);
 extern bool of_phy_is_fixed_link(struct device_node *np);
 #else