staging: comedi: usbduxfast: remove unnecessary clearing of private data

The clearing of the private data members in the (*detatch) is not
necessary. The comedi core is going to kfree the private data as soon
as the (*detach) finishes.
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/usbduxfast.c

@@ -998,16 +998,10 @@ static void usbduxfast_detach(struct comedi_device *dev)
 		usb_kill_urb(devpriv->urb);
 
 		kfree(devpriv->inbuf);
-		devpriv->inbuf = NULL;
-
 		usb_free_urb(devpriv->urb);
-		devpriv->urb = NULL;
 	}
 
 	kfree(devpriv->duxbuf);
-	devpriv->duxbuf = NULL;
-
-	devpriv->ai_cmd_running = 0;
 
 	up(&devpriv->sem);
 }