net: phy: MDIO_BCM_UNIMAC should depend on OF_MDIO

The Broadcom MDIO UniMAC driver uses routines provided by of_mdio.c which is
guarded by CONFIG_OF_MDIO.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/Kconfig

@@ -40,7 +40,7 @@ config MDIO_BCM_IPROC
 
 config MDIO_BCM_UNIMAC
 	tristate "Broadcom UniMAC MDIO bus controller"
-	depends on HAS_IOMEM
+	depends on HAS_IOMEM && OF_MDIO
 	help
 	  This module provides a driver for the Broadcom UniMAC MDIO busses.
 	  This hardware can be found in the Broadcom GENET Ethernet MAC