staging: comedi: ni_labpc_common: convert driver to use the comedi_8254 module

This driver uses an 8254 timer to generate the pacer clock used for analog
input data conversion. Convert it to use the comedi_8254 module to provide
support for the 8254 timer.

The hardware actually has two 8254 devices. Timer B0 is the master for timed
conversions, timer B1 sets the scan pacing, and tmer A0 sets the conversion
pacing.

For the conversion, dev->pacer is used for the "B" timers and a new private
data member, dev->counter, is used for the "A" timers. All the divisor values
are stored in the dev->pacer.

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>