staging: comedi: pcl812: convert driver to use the comedi_8254 module

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

Note that the pacer does not have to be stopped when starting a new async
command in pcl812_ai_cmd() or when the card is initialy reset by pcl812_reset().
The counters are all reset when the driver is initially attached and the
counters used by the pacer are stopped when a command is canceled.

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>