cpc-usb: Removed driver from staging tree

This patch prepares replacing the staging driver cpc-usb with the new
developed ems_usb CAN driver.

Signed-off-by: Sebastian Haas <haas@ems-wuensche.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: David S. Miller <davem@davemloft.net>