Really old PCMCIA cards stored the MAC address in the attribute memory
at some offset. Unlike newer cards, the MAC address wasn't part of
the CIS as a specific FUNCE. These older cards were having their MAC
address show up as 0:2:4:6:8:a because that's what's in the ROM
locations that would be there in a real ne2000.

This patch allows one to specify the offset for the MAC address for
these cards. Specify one for the IBM Ethernet II card, as it is one
that has this problem. One shouldn't specify this unless the MAC
address really isn't in the CIS at all.

Side note: The novell probe likely shouldn't read the MAC address, and
that should be moved to the bus specific attach routine(s), maybe as a
convenience function in if_ed_novell.c.

My IBM Ethernet II (aka Info Mover) now has a believable MAC address.