e1000e: alternate MAC address support

Port alternate MAC address support from the sourceforge
e1000 driver to the upstream e1000e driver.

Signed-off-by: Bill Hayes <bill.hayes@hp.com>
Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>