net: atlantic: convert EEE handling to use linkmode bitmaps

Convert EEE handling to use linkmode bitmaps. This prepares for
removing the legacy bitmaps from struct ethtool_keee.
No functional change intended.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/c5a61d57-d2b0-427f-93b3-fcf7721165f3@gmail.com


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