pcf8563: add wakeup-source support

In some platforms, the RTC is able to wake up the system but is not
directly connected to an IRQ. Add wakeup-source property support to be able
to express this in the Device Tree.

Link: https://lore.kernel.org/r/20240426225821.448963-1-alexandre.belloni@bootlin.com


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