can: usb_8dev: Add support for USB2CAN interface from 8 devices

Add device driver for USB2CAN interface from "8 devices" (http://www.8devices.com).

changes since v10:
* small cleanups

changes since v9:
* fixed syslog messages
* fixed crc error number
* increased MAX_RX_URBS and MAX_TX_URBS

changes since v8:
* remove all sysfs files

changes since v7:
* add sysfs documentation
* fix minor styling issue
* fixed can state for passive mode
* changed handling for crc errors

changes since v6:
* changed some variable types to big endian equivalent
* small cleanups

changes since v5:
* unlock mutex on error

changes since v4:
* removed FSF address
* renamed struct usb_8dev
* removed unused variable free_slots
* replaced some _to_cpu functions with pointer equivalent
* fix return value for usb_8dev_set_mode
* handle can errors with separate function
* fix overrun error handling
* rewrite error handling for usb_8dev_start_xmit
* fix urb submit in usb_8dev_start
* various small fixes

Acked-by: Wolfgang Grandegger <wg@grandegger.com>
Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Bernd Krumboeck <krumboeck@universalnet.at>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
diff --git a/drivers/net/can/usb/Kconfig b/drivers/net/can/usb/Kconfig
index acba33d..fc96a3d 100644
--- a/drivers/net/can/usb/Kconfig
+++ b/drivers/net/can/usb/Kconfig
@@ -48,4 +48,10 @@
 	  This driver supports the PCAN-USB and PCAN-USB Pro adapters
 	  from PEAK-System Technik (http://www.peak-system.com).
 
+config CAN_8DEV_USB
+	tristate "8 devices USB2CAN interface"
+	---help---
+	  This driver supports the USB2CAN interface
+	  from 8 devices (http://www.8devices.com).
+
 endmenu