cpufreq: stats: Remove redundant cpufreq_cpu_get() call

__cpufreq_stats_create_table always gets pass the valid and real policy
struct. So, there's no need to call cpufreq_cpu_get() to get the policy
again.

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