cpufreq: get rid of CONFIG_{HOTPLUG_CPU|SMP} mess

These are messing up more than the benefit they provide. It isn't
a lot of code anyway, that we will compile without them.

Kill them.

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