stmmac: mdio register has to fail if the phy is not found

With this patch the stmmac fails in case of the phy device
is not found; w/o this fix the mdio can be register twice when
do down/up the iface and this is not correct.
Reported-by: NStas <stsp@list.ru>
Signed-off-by: NGiuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c

@@ -188,8 +188,6 @@ int stmmac_mdio_register(struct net_device *ndev)
 		goto bus_register_fail;
 	}
 
-	priv->mii = new_bus;
-
 	found = 0;
 	for (addr = 0; addr < PHY_MAX_ADDR; addr++) {
 		struct phy_device *phydev = new_bus->phy_map[addr];
@@ -237,8 +235,14 @@ int stmmac_mdio_register(struct net_device *ndev)
 		}
 	}
 
-	if (!found)
+	if (!found) {
 		pr_warning("%s: No PHY found\n", ndev->name);
+		mdiobus_unregister(new_bus);
+		mdiobus_free(new_bus);
+		return -ENODEV;
+	}
+
+	priv->mii = new_bus;
 
 	return 0;