e1000: add shutdown handler back to fix WOL

Someone was waaay too aggressive and removed e1000's reboot notifier
instead of porting it to the new way of the shutdown handler.  This change
broke wake on lan.  Add the shutdown handler back in using the same method
as e100 uses.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>