ACPI: thermal: Untangle initialization and updates of active trips

Separate the code needed to update active trips (in a response to a
notification from the platform firmware) as well as to initialize them
from the code that is only necessary for their initialization and
cleanly divide it into functions that each carry out a specific action.

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