When WoL is enabled and the machine is powered off, the PHY remains
waiting for wakeup events at max speed, which is a waste of energy.

Slow down the PHY speed before stopping the ethernet if WoL is enabled,
Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Signed-off-by: David S. Miller <davem@davemloft.net>