staging: comedi: ni_labpc: sample types are unsigned

Sample values in comedi are generally represented as unsigned values.
Change the type of the `data` variable in `labpc_ai_cmd()` from `short`
to `unsigned short` for consistency.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/ni_labpc.c

@@ -893,7 +893,7 @@ static int labpc_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
 static int labpc_drain_fifo(struct comedi_device *dev)
 {
 	struct labpc_private *devpriv = dev->private;
-	short data;
+	unsigned short data;
 	struct comedi_async *async = dev->read_subdev->async;
 	const int timeout = 10000;
 	unsigned int i;