cpufreq: Remove policy create/remove notifiers

Those were added by:

commit fcd7af91 ("cpufreq: stats: handle cpufreq_unregister_driver()
and suspend/resume properly")

but aren't used anymore since:

commit 1aefc75b ("cpufreq: stats: Make the stats code non-modular").

Remove them. Also remove the redundant parameter to the respective
routines.

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