staging: comedi: ni_pcidio: 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/ni_pcidio.c

@@ -384,7 +384,7 @@ static irqreturn_t nidio_interrupt(int irq, void *d)
 {
 	struct comedi_device *dev = d;
 	struct nidio96_private *devpriv = dev->private;
-	struct comedi_subdevice *s = &dev->subdevices[0];
+	struct comedi_subdevice *s = dev->read_subdev;
 	struct comedi_async *async = s->async;
 	struct mite_struct *mite = devpriv->mite;