net: phy: respect cached advertising when re-enabling EEE

If we remove modes from EEE advertisement and disable / re-enable EEE,
then advertisement is set to all supported modes. I don't think this is
what the user expects. So respect the cached advertisement and just fall
back to all supported modes if cached advertisement is empty.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://patch.msgid.link/c75f7f8b-5571-429f-abd3-ce682d178a4b@gmail.com


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