The RTC on S2MPS13 PMIC can wakeup the system from suspend to RAM.
Add a generic property for this.

Link: https://lore.kernel.org/r/20210614193309.20248-2-krzysztof.kozlowski@canonical.comSigned-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210420164943.11152-11-krzysztof.kozlowski@canonical.comSigned-off-by: Olof Johansson <olof@lixom.net>