staging: comedi: usbdux: tidy up usbdux_ai_cancel()

Rename the local variable used for the private data pointer to the
comedi "norm".

Remove the unnecessary sanity check of the private data pointer. This
function can only be called is the private data was allocated during
the attach.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/usbdux.c

@@ -283,27 +283,19 @@ static int usbdux_ai_stop(struct comedi_device *dev, int do_unlink)
 	return ret;
 }
 
-/*
- * This will cancel a running acquisition operation.
- * This is called by comedi but never from inside the driver.
- */
 static int usbdux_ai_cancel(struct comedi_device *dev,
 			    struct comedi_subdevice *s)
 {
-	struct usbdux_private *this_usbduxsub;
-	int res = 0;
-
-	/* force unlink of all urbs */
-	this_usbduxsub = dev->private;
-	if (!this_usbduxsub)
-		return -EFAULT;
+	struct usbdux_private *devpriv = dev->private;
+	int ret = 0;
 
 	/* prevent other CPUs from submitting new commands just now */
-	down(&this_usbduxsub->sem);
+	down(&devpriv->sem);
 	/* unlink only if the urb really has been submitted */
-	res = usbdux_ai_stop(dev, this_usbduxsub->ai_cmd_running);
-	up(&this_usbduxsub->sem);
-	return res;
+	ret = usbdux_ai_stop(dev, devpriv->ai_cmd_running);
+	up(&devpriv->sem);
+
+	return ret;
 }
 
 /* analogue IN - interrupt service routine */