clocksource: clps711x: Add CLPS711X clocksource driver

This adds the clocksource driver for Cirrus Logic CLPS711X series SoCs.
Designed primarily for migration CLPS711X subarch for multiplatform & DT,
for this as the "OF" and "non-OF" calls implemented.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>