[netdrvr] forcedeth: setup wake-on-lan before shutting down

When hibernating in 'shutdown' mode, after saving the image the suspend hook
is not called again.
However, if the device is in promiscous mode, wake-on-lan will not work.
This adds a shutdown hook to setup wake-on-lan before the final shutdown.

Signed-off-by: Tobias Diedrich <ranma+kernel@tdiedrich.de>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>