[netdrvr starfire] fix highmem and broken firmware issues

Unfortunately, [your patch] might address the crash but doesn't address
the real problem. It turns out that the problem is one of padding
(the firmware cksum engine works only on 32-bit chunks, yuck), so
the special casing for length == 1 wasn't sufficient anyway.

This patch addresses the issue, as well the other issue of i386 +
CONFIG_HIGHMEM being broken. It is pretty much the same workaround
that Adaptec themselves used in their Windows driver. I have yet to
check if it fixes the problem when the skb is non-linear, but this
patch _will_ solve the problem for 99% of the users out there (those
not using sendfile).

Signed-off-by: Ion Badulescu <ionut@badula.org>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>