staging: comedi: das800: remove extra divisor calculation call
The comedi core always calls the (*do_cmdtest) function before it
calls the (*do_cmd) function. The divisors were already calculated
in das800_ai_do_cmdtest(), it is not necessary to calculate them
again in das800_ai_do_cmd().
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>