can: sja1000: remove obsolete variable open_time

The variable open_time in the struct sja1000_priv was used to protect
sja1000_set_mode() only to be called, if the interface is up. Now the CAN
device infrastructure takes care of this.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/sja1000/sja1000.h

@@ -152,7 +152,6 @@
  */
 struct sja1000_priv {
 	struct can_priv can;	/* must be the first member */
-	int open_time;
 	struct sk_buff *echo_skb;
 
 	/* the lower-layer is responsible for appropriate locking */