staging: comedi: mpc624: there are only 4 analog inputs

According to the datasheet, this board has 4 differential analog
input channels not 8. Fix the subdevice init.
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/mpc624.c

@@ -303,7 +303,7 @@ static int mpc624_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 	s = &dev->subdevices[0];
 	s->type		= COMEDI_SUBD_AI;
 	s->subdev_flags	= SDF_READABLE | SDF_DIFF;
-	s->n_chan	= 8;
+	s->n_chan	= 4;
 	s->maxdata	= 0x3fffffff;
 	s->range_table	= (it->options[1] == 0) ? &range_mpc624_bipolar1
 						: &range_mpc624_bipolar10;