ACPI: thermal: Untangle initialization and updates of the passive trip

Separate the code needed to update the passive trip (in a response to a
notification from the platform firmware) as well as to initialize it
from the code that is only necessary for its 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>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>