cpufreq: rename cpufreq_real_policy as cpufreq_user_policy

Its all about caching min/max freq requested by userspace, and
the name 'cpufreq_real_policy' doesn't fit that well. Rename it to
cpufreq_user_policy.

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