net: phy: fixed_phy: let fixed_phy_unregister free the phy_device

net: phy: fixed_phy: let fixed_phy_unregister free the phy_device

fixed_phy_register() creates and registers the phy_device. To be
symmetric, we should not only unregister, but also free the phy_device
in fixed_phy_unregister(). This allows to simplify code in users.

Note wrt of_phy_deregister_fixed_link():
put_device(&phydev->mdio.dev) and phy_device_free(phydev) are identical.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/ad8dda9a-10ed-4060-916b-3f13bdbb899d@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>