Staging: add cpc-usb driver to the staging tree

This is a CPC CAN USB driver.

Just some comments:
cpcusb.h and cpc-usb_drv.c: Essential driver source code
sja2m16c_2.c: Helper for converting bitrate timings
cpc.h: Structures and definition needed to communicate with the device

From: Sebastian Haas <haas@ems-wuensche.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>