Merge branch 'pm-domains'

* pm-domains:
  PM / Domains: Fix build warning for CONFIG_PM_RUNTIME unset
  PM / Domains: Replace plain integer with NULL pointer in domain.c file
  PM / Domains: Add missing static storage class specifier in domain.c file
  PM / Domains: Allow device callbacks to be added at any time
  PM / Domains: Add device domain data reference counter
  PM / Domains: Add preliminary support for cpuidle, v2
  PM / Domains: Do not stop devices after restoring their states
  PM / Domains: Use subsystem runtime suspend/resume callbacks by default