net: phy: fix genphy_c45_eee_is_active() for disabled EEE

net: phy: fix genphy_c45_eee_is_active() for disabled EEE

Commit 809265fe96fe ("net: phy: c45: remove local advertisement
parameter from genphy_c45_eee_is_active") stopped reading the local
advertisement from the PHY earlier in this development cycle, which
broke "ethtool --set-eee ethX eee off".

When ethtool is used to set EEE off, genphy_c45_eee_is_active()
indicates that EEE was active if the link partner reported an
advertisement, which causes phylib to set phydev->enable_tx_lpi on
link up, despite our local advertisement in hardware being empty.
However, phydev->advertising_eee is preserved while EEE is turned off,
which leads to genphy_c45_eee_is_active() incorrectly reporting that
EEE is active.

Fix it by checking phydev->eee_cfg.eee_enabled, and if clear,
immediately indicate that EEE is not active.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/E1ttmWN-0077Mb-Q6@rmk-PC.armlinux.org.uk
Signed-off-by: Paolo Abeni <pabeni@redhat.com>