thermal: cpu_cooling: store cpufreq policy

The cpufreq policy can be used by the cpu_cooling driver, lets store it
in the cpufreq_cooling_device structure.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>