thermal: core: Fix list sorting in __thermal_zone_device_update()

The order in which lists are sorted in __thermal_zone_device_update()
is reverse with respect to what it should be due to a mistake in
thermal_trip_notify_cmp().

Fix it and observe that it is not necessary to sort the lists in
different orders.  They can both be sorted in ascending order if
way_down_list is walked in reverse order which allows the code to
be slightly more straightforward (and less prone to silly mistakes).

Fixes: 7454f2c4 ("thermal: core: Sort trip point crossing notifications by temperature")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/12481676.O9o76ZdvQC@rjwysocki.net