net: phy: c45: use "supported_eee" instead of supported for access validation

Make sure we use proper variable to validate access to potentially not
supported registers. Otherwise we will get false read/write errors.

Reported-by: kernel test robot <yujie.liu@intel.com>
Link: https://lore.kernel.org/oe-lkp/202302211644.c12d19de-yujie.liu@intel.com


Fixes: 022c3f87 ("net: phy: add genphy_c45_ethtool_get/set_eee() support")
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>