can: Add driver for esd CAN-USB/2 device

This patch adds a driver for esd's USB high speed
CAN interface. The driver supports devices with
multiple CAN interfaces.

Signed-off-by: Matthias Fuchs <matthias.fuchs@esd.eu>
Acked-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: David S. Miller <davem@davemloft.net>