atl1: read MAC address from register

On some Asus motherboards containing the L1 NIC, the MAC address is
written by the BIOS directly to the MAC register during POST, and is
not stored in eeprom.  If we don't succeed in fetching the MAC address
from eeprom or spi, try reading it directly from the MAC register.
Suggested by Xiong Huang.

And do some cleanup while we've got the hood up...

Signed-off-by: Jay Cliburn <jacliburn@bellsouth.net>
Signed-off-by: Chris Snook <csnook@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>