We should not be advertising EEE for modes that we do not support,
correct that oversight by looking at the PHY device supported linkmodes.

Fixes: 99cec8a4 ("net: phy: broadcom: Allow enabling or disabling of EEE")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>