staging: comedi: adl_pci9118: cmd->stop_src == TRIG_INT is not supported

The (*do_cmdtest) only allows TRIG_COUNT, TRIG_NONE, or TRIG_EXT as the
cmd->stop_src. Remove the disabled code.

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>