cpufreq: postfix policy directory with the first CPU in related_cpus
The sysfs policy directory is postfixed currently with the CPU number
for which the policy was created, which isn't necessarily the first CPU
in related_cpus mask.
To make it more consistent and predictable, lets postfix the policy with
the first cpu in related-cpus mask.
Suggested-by: Saravana Kannan <skannan@codeaurora.org> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Reviewed-by: Saravana Kannan <skannan@codeaurora.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>