thermal: core: move power actor code out of sysfs I/F section

Simply reorganize code to keep only functions of sysfs interface
of thermal zone device together. Therefore, move the power actor code
out of the sysfs I/F section.

Cc: Zhang Rui <rui.zhang@intel.com>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>