staging: comedi: ni_tiocmd: remove unsed param from ni_tio_acknowledge_and_confirm()

The 'stale_data' pointer is always NULL. Just remove it.

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>