soc: nordic: nrf54h20: enable PM_DEVICE_RUNTIME if PM by default

PM on the nrf54h20 has minimal utility if power domains and devices
are not managed at runtime, as these prevent the soc from entering
sleep states in the first place. Enable PM_DEVICE by default if PM,
which in turn enables PM_DEVICE_RUNTIME for devices and power
domains.

Signed-off-by: Bjarki Arge Andreasen <bjarki.andreasen@nordicsemi.no>