To iterate over all policies we currently iterate over all CPUs and
then get the policy for each of them.  Let's use the newly created
cpufreq_policy_list for this purpose.

[rjw: Changelog]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>