thermal: core: Prepare for moving trips between sorted lists

Subsequently, trips will be moved between sorted lists in multiple
places, so replace add_trip_to_sorted_list() with an analogous
function, move_trip_to_sorted_list(), that will move a given trip
to a given sorted list.

To allow list_del() used in the new function to work, initialize the
list_node fields in trip descriptors where applicable so they are
always valid.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://patch.msgid.link/2960197.e9J7NaK4W3@rjwysocki.net