can: ems_usb: remove obsolete variable open_time

The variable open_time in the struct ems_usb was used to protect
ems_usb_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/usb/ems_usb.c

@@ -245,7 +245,6 @@ struct ems_tx_urb_context {
 
 struct ems_usb {
 	struct can_priv can; /* must be the first member */
-	int open_time;
 
 	struct sk_buff *echo_skb[MAX_TX_URBS];
 
@@ -728,7 +727,6 @@ static int ems_usb_open(struct net_device *netdev)
 		return err;
 	}
 
-	dev->open_time = jiffies;
 
 	netif_start_queue(netdev);
 
@@ -878,8 +876,6 @@ static int ems_usb_close(struct net_device *netdev)
 
 	close_candev(netdev);
 
-	dev->open_time = 0;
-
 	return 0;
 }
 
@@ -905,9 +901,6 @@ static int ems_usb_set_mode(struct net_device *netdev, enum can_mode mode)
 {
 	struct ems_usb *dev = netdev_priv(netdev);
 
-	if (!dev->open_time)
-		return -EINVAL;
-
 	switch (mode) {
 	case CAN_MODE_START:
 		if (ems_usb_write_mode(dev, SJA1000_MOD_NORMAL))