ARCNET: add support for multi interfaces on com20020

The com20020-pci driver is currently designed to instance
one netdev with one pci device. This patch adds support to
instance many cards with one pci device, depending on the device
data in the private data.

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