net: phy: start using genphy_c45_ethtool_get/set_eee()

All preparations are done. Now we can start using new functions and remove
the old code.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>