thermal: mediatek: Add cpu dynamic power cooling model.

MT8173 cpufreq driver select of_cpufreq_power_cooling_register registering
cooling devices with dynamic power coefficient.

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Dawei Chien <dawei.chien@mediatek.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>