net: ethtool: eee: Remove legacy _u32 from keee

All MAC drivers have been converted to use the link mode members of
keee. So remove the _u32 values, and the code in the ethtool core to
convert the legacy _u32 values to link modes.

Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>