clocksource/drivers/realtek: Add timer driver for rtl-otto platforms

clocksource/drivers/realtek: Add timer driver for rtl-otto platforms

The timer/counter block on the Realtek SoCs provides up to 5 timers. It
also includes a watchdog timer which is handled by the
realtek_otto_wdt.c driver.

One timer will be used per CPU as a local clock event generator. An
additional timer will be used as an overal stable clocksource.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Signed-off-by: Sander Vanheule <sander@svanheule.net>
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Link: https://lore.kernel.org/r/20240710043524.1535151-8-chris.packham@alliedtelesis.co.nz
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>