netdev/phy: Prototype of_mdio_find_bus()

Ensure that of_mdio_find_bus() matches the prototype in the header (and
stop sparse complaining) by including the header with the prototype.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/mdio_bus.c

@@ -26,6 +26,7 @@
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/of_device.h>
+#include <linux/of_mdio.h>
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/skbuff.h>