can: add socket type for CAN_J1939

This patch is a preparation for SAE J1939 and adds CAN_J1939
socket type.

Signed-off-by: Kurt Van Dijck <dev.kurt@vandijck-laurijssen.be>
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

Author: kurt-vd

include/uapi/linux/can.h

@@ -157,7 +157,8 @@ struct canfd_frame {
 #define CAN_TP20	4 /* VAG Transport Protocol v2.0 */
 #define CAN_MCNET	5 /* Bosch MCNet */
 #define CAN_ISOTP	6 /* ISO 15765-2 Transport Protocol */
-#define CAN_NPROTO	7
+#define CAN_J1939	7 /* SAE J1939 */
+#define CAN_NPROTO	8
 
 #define SOL_CAN_BASE 100