Add detach routine and turn driver into a module so it can be loaded
and unloaded. Also take a stab at implementing multicast packet
reception so that this NIC will work with IPv6. Promiscuous mode
doesn't seem to work, but I'm not sure why. It works well enough that
I can run dhclient on it and put it on the office network though.
Also ripped out spl stuff and replaced it with mutexes.
