staging: comedi: dt2815: remove subdevice pointer math

Convert the comedi_subdevice access from pointer math to array
access.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/dt2815.c

@@ -185,7 +185,7 @@ static int dt2815_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 	if (alloc_private(dev, sizeof(struct dt2815_private)) < 0)
 		return -ENOMEM;
 
-	s = dev->subdevices;
+	s = &dev->subdevices[0];
 	/* ao subdevice */
 	s->type = COMEDI_SUBD_AO;
 	s->subdev_flags = SDF_WRITABLE;