clocksource/drivers/ingenic: Add support for the Ingenic X1000 OST.

X1000 and SoCs after X1000 (such as X1500 and X1830) had a separate
OST, it no longer belongs to TCU. This driver will register both a
clocksource and a sched_clock to the system.

Tested-by: 周正 (Zhou Zheng) <sernia.zhou@foxmail.com>
Co-developed-by: 漆鹏振 (Qi Pengzhen) <aric.pzqi@ingenic.com>
Signed-off-by: 漆鹏振 (Qi Pengzhen) <aric.pzqi@ingenic.com>
Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>
Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200722171804.97559-3-zhouyanjie@wanyeetech.com