drivers: pps: Make PPS into a menuconfig to ease disabling

So that there's no need to get into the submenu to disable all related config
entries.

The BROKEN PPS_GENERATOR_PARPORT now also depends on PPS

Signed-off-by: Vincent Legoll <vincent.legoll@gmail.com>
Acked-by: Rodolfo Giometti <giometti@enneenne.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>