staging: comedi: pcl711: use dev->read_subdev in interrupt handler

The comedi_subdevice used in the interrupt handler is the dev->read_subdev
that was initialized during the attach of the board. Use that instead of
accessing the dev->subdevices array directly.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/pcl711.c

@@ -201,7 +201,7 @@ static irqreturn_t pcl711_interrupt(int irq, void *d)
 	struct comedi_device *dev = d;
 	const struct pcl711_board *board = comedi_board(dev);
 	struct pcl711_private *devpriv = dev->private;
-	struct comedi_subdevice *s = &dev->subdevices[0];
+	struct comedi_subdevice *s = dev->read_subdev;
 	unsigned int data;
 
 	if (!dev->attached) {