staging: comedi: amplc_pc236: use dev->read_subdev

Use the dev->read_subdev that was setup in the device attach 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/amplc_pc236.c

@@ -356,7 +356,7 @@ static int pc236_intr_cancel(struct comedi_device *dev,
 static irqreturn_t pc236_interrupt(int irq, void *d)
 {
 	struct comedi_device *dev = d;
-	struct comedi_subdevice *s = &dev->subdevices[1];
+	struct comedi_subdevice *s = dev->read_subdev;
 	int handled;
 
 	handled = pc236_intr_check(dev);