can: fix SJA1000 dlc for RTR packets

can: fix SJA1000 dlc for RTR packets

BugLink: http://bugs.launchpad.net/bugs/788691

commit 87e9af6cc67d842cd92b52b81f3f14e665e7ab05 upstream.

RTR frames do have a valid data length code on CAN.
The driver for SJA1000 did not handle that situation properly.

Signed-off-by: Kurt Van Dijck <kurt.van.dijck@eia.be>
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Steve Conklin <sconklin@canonical.com>