cpufreq / governor: Remove fossil comment

cpufreq_set_policy() has been changed to origin __cpufreq_set_policy()
and policy->lock has been converted to rewrite lock by commit 5a01f2.
So remove the comment.

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