Thermal: Remove throttling logic out of thermal_sys.c

This patch removes the throttling logic out of
thermal_sys.c; also refactors the code into smaller
functions so that are easy to read/maintain.
 * Seperates the handling of critical and non-critical trips
 * Re-arranges the set_polling and device_check methods, so
   that all related functions are arranged in one place.
 * Removes the 'do_update' and 'trip_update' method, as part
   of moving the throttling logic out of thermal_sys.c

Signed-off-by: Durgadoss R <durgadoss.r@intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>