arcnet: com20020-pci: add support for PCIFB2 card

We add support for the PCIFB2 card from EAE.

Beside other cards, this card has the backplane mode enabled by default.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>