dt-bindings: rtc: qcom-pm8xxx: allow 'wakeup-source' property

The RTC can be used as a wakeup source on at least some platforms so
allow it to be described as such.

Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230104095612.6756-1-johan+linaro@kernel.org


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