cpufreq: stats: Change return type of cpufreq_stats_update() as void

It always returns 0 and none of its callers check its return value. Make
it return void.

Change-Id: I1fca4f037bac103602c43c05b0bab4a518469160
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Git-repo: https://android.googlesource.com/kernel/common/


Git-commit: d476ec4f7f5aba47b0a570cbf659d7330d7e71c
Signed-off-by: Rahul Shahare <rshaha@codeaurora.org>