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

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

This reverts commit 4e2178342d39c7b7f57f2b9e953fa8a8a407af7d.

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>