staging: comedi: comedi_test: remove unnecessary del_timer() call

In the "comedi_test" module, the timer function
`waveform_ai_interrupt()` doesn't need to remove the timer from the
timer queue as the caller has already removed it from the queue.  Remove
the call to `del_timer()` in this function.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/comedi_test.c

@@ -218,8 +218,6 @@ static void waveform_ai_interrupt(unsigned long arg)
 
 	if ((async->events & COMEDI_CB_EOA) == 0 && devpriv->timer_running)
 		mod_timer(&devpriv->timer, jiffies + 1);
-	else
-		del_timer(&devpriv->timer);
 
 	comedi_event(dev, dev->read_subdev);
 }