pm: system: Suspend devices on STATE_SOFT_OFF
pm: system: Suspend devices on STATE_SOFT_OFF

Suspend devices when the system goes to STATE_SOFT_OFF.
This state was not triggering any device power management. This should
at least suspend devices as it is done for SUSPEND_TO_RAM and
SUSPEND_TO_DISK.

Signed-off-by: Flavio Ceolin <979b9165500b0741b9d0500e2efd74fc1547bff7@intel.com>

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