cpufreq: governor: Make dbs_data_mutex static
That mutex is only used by cpufreq_governor_dbs() and it doesn't
need to be exported to modules, so make it static and drop the
export incantation.
No functional changes.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>