[b44] Add driver for Broadcom bcm44xx cards

This driver is based on Stefan Hajnoczi's summer work, which
is in turn based on version 1.01 of the linux b44 driver.
I just assembled the pieces and fixed/added a few pieces
here and there to make it work for my hardware.

The most major limitation is that this driver won't work
on systems with >1GB RAM due to the card not having enough
address bits for that and gPXE not working around this
limitation.

Still, other than that the driver works well enough for
at least 2 users :) and the above limitation can always
be fixed when somebody wants it bad enough :)

Signed-off-by: Pantelis Koukousoulas <[email protected]>