PC300too alternative WAN driver

The attached patch adds an alternative driver "pc300too" for PCI WAN
cards PC300/RSV and PC300/X21 made by Cyclades Corp. (now Avocent Corp).

Signed-off-by: Krzysztof Halasa <khc@pm.waw.pl>
Signed-off-by: Jeff Garzik <jeff@garzik.org>