atl1: save mac address on remove

Some atl1 boards get their MAC address written directly to the register
by the BIOS during POST, rather than storing it in EEPROM that's
accessible to the driver.  If the MAC register on one of these boards
is changed and then the module is unloaded, the permanent MAC address
will be forgotten until the box is rebooted.  We should save the
permanent address during removal if we've been messing with it.

Signed-off-by: Chris Snook <csnook@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>