staging: comedi: usbduxsigma: check for invalid 'ao_timer' in all cases

Make sure to check that the 'ao_timer' value is valid for both the
high speed and low speed cases in usbduxsigma_ao_cmdtest().
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/usbduxsigma.c

@@ -994,9 +994,9 @@ static int usbduxsigma_ao_cmdtest(struct comedi_device *dev,
 		 * we get all channels at once
 		 */
 		devpriv->ao_timer = cmd->scan_begin_arg / 1000000;
+	}
 	if (devpriv->ao_timer < 1)
 		err |= -EINVAL;
-	}
 
 	if (cmd->stop_src == TRIG_COUNT) {
 		/* not continuous, use counter */