can: at91_can: add missing prepare and unprepare of the clock

In order to make the driver work with the common clock framework, this patch
converts the clk_enable()/clk_disable() to
clk_prepare_enable()/clk_disable_unprepare(). While there, add the missing
error handling.
Signed-off-by: David Dueck <davidcdueck@googlemail.com>
Signed-off-by: Anthony Harivel <anthony.harivel@emtrion.de>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/at91_can.c

@@ -1123,7 +1123,9 @@ static int at91_open(struct net_device *dev)
 	struct at91_priv *priv = netdev_priv(dev);
 	int err;
 
-	clk_enable(priv->clk);
+	err = clk_prepare_enable(priv->clk);
+	if (err)
+		return err;
 
 	/* check or determine and set bittime */
 	err = open_candev(dev);
@@ -1149,7 +1151,7 @@ static int at91_open(struct net_device *dev)
  out_close:
 	close_candev(dev);
  out:
-	clk_disable(priv->clk);
+	clk_disable_unprepare(priv->clk);
 
 	return err;
 }
@@ -1166,7 +1168,7 @@ static int at91_close(struct net_device *dev)
 	at91_chip_stop(dev, CAN_STATE_STOPPED);
 
 	free_irq(dev->irq, dev);
-	clk_disable(priv->clk);
+	clk_disable_unprepare(priv->clk);
 
 	close_candev(dev);