staging: comedi: usbdux: tidy up usbdux_ao_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

@@ -449,22 +449,19 @@ static int usbdux_ao_stop(struct comedi_device *dev, int do_unlink)
 	return ret;
 }
 
-/* force unlink, is called by comedi */
 static int usbdux_ao_cancel(struct comedi_device *dev,
 			    struct comedi_subdevice *s)
 {
-	struct usbdux_private *this_usbduxsub = dev->private;
-	int res = 0;
-
-	if (!this_usbduxsub)
-		return -EFAULT;
+	struct usbdux_private *devpriv = dev->private;
+	int ret = 0;
 
 	/* prevent other CPUs from submitting a command just now */
-	down(&this_usbduxsub->sem);
+	down(&devpriv->sem);
 	/* unlink only if it is really running */
-	res = usbdux_ao_stop(dev, this_usbduxsub->ao_cmd_running);
-	up(&this_usbduxsub->sem);
-	return res;
+	ret = usbdux_ao_stop(dev, devpriv->ao_cmd_running);
+	up(&devpriv->sem);
+
+	return ret;
 }
 
 static void usbduxsub_ao_isoc_irq(struct urb *urb)