phy: Add API for {un}registering an mdio device to a bus.

Rather than have drivers directly manipulate the mii_bus structure,
provide and API for registering and unregistering devices on an MDIO
bus, and performing lookups.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index da255fb..502da6f 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -48,6 +48,7 @@
 #include <linux/irq.h>
 #include <linux/clk.h>
 #include <linux/platform_device.h>
+#include <linux/mdio.h>
 #include <linux/phy.h>
 #include <linux/fec.h>
 #include <linux/of.h>
@@ -1926,11 +1927,7 @@
 	} else {
 		/* check for attached phy */
 		for (phy_id = 0; (phy_id < PHY_MAX_ADDR); phy_id++) {
-			if ((fep->mii_bus->phy_mask & (1 << phy_id)))
-				continue;
-			if (fep->mii_bus->phy_map[phy_id] == NULL)
-				continue;
-			if (fep->mii_bus->phy_map[phy_id]->phy_id == 0)
+			if (!mdiobus_is_registered_device(fep->mii_bus, phy_id))
 				continue;
 			if (dev_id--)
 				continue;