clocksource: Ingenic: Add SMP/SMT support for sysost driver.

1.The OST in Ingenic XBurst®2 SoCs has a global timer and
  up to 16 event timers, add support for the event timers.
2.Add compatible strings for the X1600 SoC, the X1830 SoC,
  the X2000 SoC, and the X2500 SoC.

Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>