Record surfaceflinger power_service access.

Address the following log entry:
SELinux : avc:  granted  { find } for service=power scontext=u:r:surfaceflinger:s0 tcontext=u:object_r:power_service:s0 tclass=service_manager

Change-Id: Id750ba9f99c622351fb3206ad007eae8a713adea