net: phy: smsc: use device-managed clock API

Simplify the code by using the device-managed clock API.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/b222be68-ba7e-999d-0a07-eca0ecedf74e@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>