net-next: mediatek: use mdiobus_free() in favour of kfree()

The driver currently uses kfree() to clear the mii_bus. This is not the
correct way to clear the memory and mdiobus_free() should be used instead.
This patch fixes the two instances where this happens in the driver.
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: John Crispin <john@phrozen.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mediatek/mtk_eth_soc.c

@@ -280,7 +280,7 @@ static int mtk_mdio_init(struct mtk_eth *eth)
 	return 0;
 
 err_free_bus:
-	kfree(eth->mii_bus);
+	mdiobus_free(eth->mii_bus);
 
 err_put_node:
 	of_node_put(mii_np);
@@ -295,7 +295,7 @@ static void mtk_mdio_cleanup(struct mtk_eth *eth)
 
 	mdiobus_unregister(eth->mii_bus);
 	of_node_put(eth->mii_bus->dev.of_node);
-	kfree(eth->mii_bus);
+	mdiobus_free(eth->mii_bus);
 }
 
 static inline void mtk_irq_disable(struct mtk_eth *eth, u32 mask)