can: c_can: end pending transmission on network stop (ifdown)

commit 7ffd7b4e upstream.

Put controller into init mode in network stop to end pending transmissions. The
issue is observed in cases when transmitted frame is not acked.
Signed-off-by: Viktor Babrian <babrian.viktor@renyi.mta.hu>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/net/can/c_can/c_can.c

@@ -611,6 +611,10 @@ static void c_can_stop(struct net_device *dev)
 	struct c_can_priv *priv = netdev_priv(dev);
 
 	c_can_irq_control(priv, false);
+
+	/* put ctrl to init on stop to end ongoing transmission */
+	priv->write_reg(priv, C_CAN_CTRL_REG, CONTROL_INIT);
+
 	priv->can.state = CAN_STATE_STOPPED;
 }