net: mdiobus: fix unbalanced node reference count

I got the following report while doing device(mscc-miim) load test
with CONFIG_OF_UNITTEST and CONFIG_OF_DYNAMIC enabled:

  OF: ERROR: memory leak, expected refcount 1 instead of 2,
  of_node_get()/of_node_put() unbalanced - destroy cset entry:
  attach overlay node /spi/soc@0/mdio@7107009c/ethernet-phy@0

If the 'fwnode' is not an acpi node, the refcount is get in
fwnode_mdiobus_phy_device_register(), but it has never been
put when the device is freed in the normal path. So call
fwnode_handle_put() in phy_device_release() to avoid leak.

If it's an acpi node, it has never been get, but it's put
in the error path, so call fwnode_handle_get() before
phy_device_register() to keep get/put operation balanced.

Fixes: bc1bee3 ("net: mdiobus: Introduce fwnode_mdiobus_register_phy()")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20221124150130.609420-1-yangyingliang@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/mdio/fwnode_mdio.c

@@ -148,7 +148,7 @@ int fwnode_mdiobus_register_phy(struct mii_bus *bus,
 		/* Associate the fwnode with the device structure so it
 		 * can be looked up later.
 		 */
-		phy->mdio.dev.fwnode = child;
+		phy->mdio.dev.fwnode = fwnode_handle_get(child);
 
 		/* All data is now stored in the phy struct, so register it */
 		rc = phy_device_register(phy);

drivers/net/phy/phy_device.c

@@ -217,6 +217,7 @@ static void phy_mdio_device_free(struct mdio_device *mdiodev)
 
 static void phy_device_release(struct device *dev)
 {
+	fwnode_handle_put(dev->fwnode);
 	kfree(to_phy_device(dev));
 }