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

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

This reverts commit a67a46af4ad6342378e332b7420c1d1a2818c53f.

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>