Revert "thermal/core: Deprecate changing cooling device state from userspace"

Revert "thermal/core: Deprecate changing cooling device state from userspace"

This reverts commit 78b694bc47247b4c552ea90f1eae33f826b4e4f3.

It has been reported the warning is annoying as the cooling device
state is still needed on some production system.

Meanwhile we provide a way to consolidate the thermal framework to
prevent multiple actors acting on the cooling devices with conflicting
decisions, let's revert this warning.

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