r8169: switch to new function phy_support_eee

Switch to new function phy_support_eee. This allows to simplify
the code because data->tx_lpi_enabled is now populated by
phy_ethtool_get_eee().

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/92462328-5c9b-4d82-9ce4-ea974cda4900@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>