sky2: WoL changes

Change Wake On Lan code to be similar to vendor driver. The definition
of Y2_HW_WOL_ON is confusing; what it means is transition to firmware SPI
setting when doing power change.

Since same code is done for both shutdown and suspend, use common
code path.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>