net: phy: c45: genphy_c45_ethtool_set_eee: validate EEE link modes

Currently, it is possible to let some PHYs to advertise not supported
EEE link modes. So, validate them before overwriting existing
configuration.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>