thermal: core: move the trip attrs to the tz sysfs I/F section

Code reorganization to keep all the sysfs I/F of a thermal zone in the
same 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>