of/mdio: Staticise !CONFIG_OF stubs

The !CONFIG_OF stubs aren't static so if multiple files include the
header with this configuration then the linker will see multiple
definitions of the stubs.
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/of_mdio.h

@@ -26,17 +26,17 @@ extern struct phy_device *of_phy_connect_fixed_link(struct net_device *dev,
 extern struct mii_bus *of_mdio_find_bus(struct device_node *mdio_np);
 
 #else /* CONFIG_OF */
-int of_mdiobus_register(struct mii_bus *mdio, struct device_node *np)
+static inline int of_mdiobus_register(struct mii_bus *mdio, struct device_node *np)
 {
 	return -ENOSYS;
 }
 
-struct phy_device *of_phy_find_device(struct device_node *phy_np)
+static inline struct phy_device *of_phy_find_device(struct device_node *phy_np)
 {
 	return NULL;
 }
 
-struct phy_device *of_phy_connect(struct net_device *dev,
+static inline struct phy_device *of_phy_connect(struct net_device *dev,
 						struct device_node *phy_np,
 						void (*hndlr)(struct net_device *),
 						u32 flags, phy_interface_t iface)
@@ -44,14 +44,14 @@ struct phy_device *of_phy_connect(struct net_device *dev,
 	return NULL;
 }
 
-struct phy_device *of_phy_connect_fixed_link(struct net_device *dev,
+static inline struct phy_device *of_phy_connect_fixed_link(struct net_device *dev,
 							   void (*hndlr)(struct net_device *),
 							   phy_interface_t iface)
 {
 	return NULL;
 }
 
-struct mii_bus *of_mdio_find_bus(struct device_node *mdio_np)
+static inline struct mii_bus *of_mdio_find_bus(struct device_node *mdio_np)
 {
 	return NULL;
 }