EEE should be only be enabled during stmmac_mac_link_up() when the
link are up and being set up properly. set_eee should only do settings
configuration and disabling the eee.

Without this fix, turning on EEE using ethtool will return
"Operation not supported". This is due to the driver is in a dead loop
waiting for eee to be advertised in the for eee to be activated but the
driver will only configure the EEE advertisement after the eee is
activated.

Ethtool should only return "Operation not supported" if there is no EEE
capbility in the MAC controller.

Fixes: 8a7493e5 ("net: stmmac: Fix a race in EEE enable callback")
Signed-off-by: Voon Weifeng <weifeng.voon@intel.com>
Acked-by: Mark Gross <mgross@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>