atl1: add shutdown callback

Add a shutdown callback that points to atl1_suspend().  This, along
with a working suspend function, fixes wake-on-lan.

Tested-by: Per Olofsson <pelle@dsv.su.se>
Signed-off-by: Jay Cliburn <jacliburn@bellsouth.net>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>