cpufreq: Restart governor as soon as possible

__cpufreq_remove_dev_finish() is doing two things today:
- Restarts the governor if some CPUs from concerned policy are still
  online.
- Frees the policy if all CPUs are offline.

The first task of restarting the governor can be moved to
__cpufreq_remove_dev_prepare() to restart the governor early. There is
no race between _prepare() and _finish() as they would be handling
completely different cases. _finish() will only be required if we are
going to free the policy and that has nothing to do with restarting the
governor.

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