After moving the DB8500 thermal driver to use device tree
we define the default thermal zone for the Ux500 in the
device tree replacing the oldstyle hardcoded trigger
points.

This default thermal zone utilizes the cpufreq driver
(using the generic OF cpufreq back-end) as a passive
cooling device, and defines a critical trip point when
the temperature goes above 85 degrees celsius which will
(hopefully) make the system shut down if the temperature
cannot be controlled.

This default policy can later be augmented for specific
subdevices if these have tighter temperature conditions.

After this patch we get:

/sys/class/thermal/thermal_zone0 (CPU thermal zone)
This reports the rough temperature and trip points
from the thermal zone in the device tree.

By executing two yes > /dev/null & jobs fully utilizing
the two CPU cores we can notice the temperature climbing
in the thermal zone in response and falling when we kill
the jobs.

/syc/class/thermal/cooling_device0 (cpufreq cooling)
this reports all 4 available cpufreq frequencies as
states.
Suggested-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>