rtc: support for the Amlogic on-chip RTC

rtc: support for the Amlogic on-chip RTC

This is the third amlogic driver. The RTC hardware of A4 SoC is different
from the previous one. This RTC hardware includes a timing function and
an alarm function. But the existing has only timing function, alarm
function is using the system clock to implement a virtual alarm. Add
the RTC driver to support it.

Signed-off-by: Yiting Deng <yiting.deng@amlogic.com>
Signed-off-by: Xianwei Zhao <xianwei.zhao@amlogic.com>
Link: https://lore.kernel.org/r/20241112-rtc-v6-2-a71b60d2f354@amlogic.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>