net: stmmac: remove redundant code from ethtool EEE ops

net: stmmac: remove redundant code from ethtool EEE ops

Setting edata->tx_lpi_enabled in stmmac_ethtool_op_get_eee() gets
overwritten by phylib, so there's no point setting this.

In stmmac_ethtool_op_set_eee(), now that stmmac is using the result of
phylib's evaluation of EEE, there is no need to handle anything in the
ethtool EEE ops other than calling through to the appropriate phylink
function, which will pass on to phylib the users request.

As stmmac_disable_eee_mode() is now no longer called from outside
stmmac_main.c, make it static.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Choong Yong Liang <yong.liang.choong@linux.intel.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1tVZDr-0002KF-Cv@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>