net: mdio: fix unbalanced fwnode reference count in mdio_device_release()

There is warning report about of_node refcount leak
while probing mdio device:

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@710700c0/ethernet@4

In of_mdiobus_register_device(), we increase fwnode refcount
by fwnode_handle_get() before associating the of_node with
mdio device, but it has never been decreased in normal path.
Since that, in mdio_device_release(), it needs to call
fwnode_handle_put() in addition instead of calling kfree()
directly.

After above, just calling mdio_device_free() in the error handle
path of of_mdiobus_register_device() is enough to keep the
refcount balanced.

Fixes: a9049e0c ("mdio: Add support for mdio drivers.")
Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/20221203073441.3885317-1-zengheng4@huawei.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/mdio/of_mdio.c

@@ -68,8 +68,9 @@ static int of_mdiobus_register_device(struct mii_bus *mdio,
 	/* All data is now stored in the mdiodev struct; register it. */
 	rc = mdio_device_register(mdiodev);
 	if (rc) {
+		device_set_node(&mdiodev->dev, NULL);
+		fwnode_handle_put(fwnode);
 		mdio_device_free(mdiodev);
-		of_node_put(child);
 		return rc;
 	}
 

drivers/net/phy/mdio_device.c

@@ -21,6 +21,7 @@
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/unistd.h>
+#include <linux/property.h>
 
 void mdio_device_free(struct mdio_device *mdiodev)
 {
@@ -30,6 +31,7 @@ EXPORT_SYMBOL(mdio_device_free);
 
 static void mdio_device_release(struct device *dev)
 {
+	fwnode_handle_put(dev->fwnode);
 	kfree(to_mdio_device(dev));
 }