Require 3 readings for same status before changing thermal status

We have seen problems in thermal readings that one error reading with high temperature will shut down the device. This change requires 3 readings in new thermal status level before it is accepted. While taking these readings, we use accelerated reading frequency so that transition to new level does not take too much time.

Signed-off-by: Pekka Lundstrom <pekka.lundstrom@jollamobile.com>