tools: gpio: add support for reporting realtime event clock to lsgpio

Add support for reporting if a line is configured to report realtime
timestamps in events.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Link: https://lore.kernel.org/r/20201014231158.34117-3-warthog618@gmail.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>