thermal: cpu_cooling: Pass 'cpufreq_dev' to get_property()

We already know the value of 'cpufreq_dev->max_level' and so there is no need
calculating that once again. For this, we need to send 'cpufreq_dev' to
get_property().

Make all necessary changes for this change. Because cpufreq_cooling_get_level()
doesn't have access to 'cpufreq_dev', it is updated to iterate over the list of
cpufreq_cooling_devices to get cooling device for the cpu number passed to it.
This also makes it robust to return levels only for the CPU registered via a
cooling device. We don't have to support anything that isn't registered yet.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>