can: usb: PEAK-System Technik PCAN-USB Pro specific part

This patch adds the specific part which handles the PCAN-USB Pro adapter
from PEAK-System Technik (http://www.peak-system.com). The PCAN-USB Pro
adapter is a dual-channel USB 2.0 adapter compliant with CAN specifications

Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Acked-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: Stephane Grosjean <s.grosjean@peak-system.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>