pps-gpio: Allow enabling the option 'capture_clear' from the device tree

[Marek Szuba]

Hello,

It has been possible to switch asserts from the rising to the falling
edge via the DT for quite a while so it would be nice to be able to do
the same with generating clear events - it is useful for improving
timing precision under some circumstances. Any chance we could have this
feature added to mainline kernels some time soon? It is a pretty trivial
change, see e.g.

https://github.com/raspberrypi/linux/commit/486a3a1dfa5e7892522d18b62aa33219a1b1ad31

and in addition to the Raspberry Pi, this seems to work fine on my
Allwinner A20-based SBC with (patched and self-built, of course) kernel 5.8.

What do you think?

Cheers,
-- 
MS