ACPI: thermal: Combine passive and active trip update functions

Combine acpi_thermal_update_passive_trip() and
acpi_thermal_update_active_trip() into one common function called
acpi_thermal_update_trip(), so as to reduce code duplication and
prepare the code in question for subsequent changes.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>