net: phy: dp83640: improve phydev and driver removal handling

net: phy: dp83640: improve phydev and driver removal handling

Once the last user of a clock has been removed, the clock should be
removed. So far orphaned clocks are cleaned up in dp83640_free_clocks()
only. Add the logic to remove orphaned clocks in dp83640_remove().
This allows to simplify the code, and use standard macro
module_phy_driver(). dp83640 was the last external user of
phy_driver_register(), so we can stop exporting this function afterwards.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/6d4e80e7-c684-4d95-abbd-ea62b79a9a8a@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>