net: phy: update phy_ethtool_get_eee() documentation

Update the phy_ethtool_get_eee() documentation to make it clear that
all members of struct ethtool_keee are written by this function.

keee.supported, keee.advertised, keee.lp_advertised and keee.eee_active
are all written by genphy_c45_ethtool_get_eee().

keee.tx_lpi_timer, keee.tx_lpi_enabled and keee.eee_enabled are all
written by eeecfg_to_eee().

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/E1tJ9JH-006LIz-SO@rmk-PC.armlinux.org.uk


Signed-off-by: Jakub Kicinski <kuba@kernel.org>