drivers: irtc: Updated rtc driver to support NXP RT700 device.

1. Update nxp irtc driver to fix issue in init and alarm function.
2. Update RTC device tree binding to support "share-counter".
3. Update RT700 dtsi to support rtc0 for cpu0 and rtc1 for cpu1.
4. Update readme.
5. Update unit test project conf for RT700.

Signed-off-by: Holt Sun <holt.sun@nxp.com>