staging: comedi: adl_pci9111: remove extra i8253_cascade_ns_to_timer_2div()

The comedi core always calls the 'do_cmdtest' function before it
calls the 'do_cmd' function. The 'do_cmdtest' for this driver calls
i8253_cascade_ns_to_timer_2div() to validate the cmd->convert_arg.
This call sets the dev_private 'div1' and 'div2' values needed to
program the 8254 timer. There is no need to call the i8253 function
a second time in the do_cmd function.

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>