thermal: uniphier: Use thermal_zone_for_each_trip() for walking trip points

thermal: uniphier: Use thermal_zone_for_each_trip() for walking trip points

It is generally inefficient to iterate over trip indices and call
thermal_zone_get_trip() every time to get the struct thermal_trip
corresponding to the given trip index, so modify the uniphier thermal
driver to use thermal_zone_for_each_trip() for walking trips.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Link: https://patch.msgid.link/2148114.bB369e8A3T@kreacher
[ rjw: Add missing return statement, remove unused local variable ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>