staging: comedi: das08: convert driver to use the comedi_8254 module

Some of the hardware supported by this driver include an 8254 timer that is
exposed to the user as a comedi_subdevice. Convert it to use the comedi_8254
module to provide support for the 8254 timer.

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>