staging: comedi: ni_6527: use dev->read_subdev in interrupt handler

The comedi_subdevice in the interrupt handler is the dev->read_subdev
that was initialized during the attach. 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/ni_6527.c

@@ -205,7 +205,7 @@ static irqreturn_t ni6527_interrupt(int irq, void *d)
 {
 	struct comedi_device *dev = d;
 	struct ni6527_private *devpriv = dev->private;
-	struct comedi_subdevice *s = &dev->subdevices[2];
+	struct comedi_subdevice *s = dev->read_subdev;
 	unsigned int status;
 
 	status = readb(devpriv->mite->daq_io_addr + Change_Status);