cpufreq: Call __cpufreq_governor() with correct policy->cpus mask

__cpufreq_governor() must be called with a correct policy->cpus mask.
In __cpufreq_remove_dev() we initially clear policy->cpus with
cpumask_clear_cpu() and then call
__cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT). If the governor
is doing some per-cpu stuff in EXIT callback, this can create
uncertain behavior.

Generic governors in drivers/cpufreq/ doesn't do any per-cpu stuff
in EXIT callback and so we don't face any issues currently. But its
better to keep the code clean, so we don't face any issues in future.

Now, we call cpumask_clear_cpu() only when multiple cpus are managed
by policy.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cpufreq.c

@@ -1105,7 +1105,9 @@ static int __cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif
 
 	WARN_ON(lock_policy_rwsem_write(cpu));
 	cpus = cpumask_weight(data->cpus);
-	cpumask_clear_cpu(cpu, data->cpus);
+
+	if (cpus > 1)
+		cpumask_clear_cpu(cpu, data->cpus);
 	unlock_policy_rwsem_write(cpu);
 
 	if (cpu != data->cpu) {