staging: comedi: pcl812: don't calc the timer divisors twice

staging: comedi: pcl812: don't calc the timer divisors twice

The timer divisors are calculated in the (*do_cmdtest) before the (*do_cmd)
is called by the comedi core. Save the values in the private data so they
don't need to be recalced.

Refactor pcl812_start_pacer() to use the values from the private data.

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>