rtc: rv8803: Add power management support

Add power management support to the driver. This allows a SoC to wake
from suspend using the nINT provided by the RTC. Only register it as a
wakeup device if the interrupt is provided and handled.

Signed-off-by: Stefan Eichenberger <eichest@gmail.com>
Link: https://lore.kernel.org/r/20231122181611.164792-1-eichest@gmail.com


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>