cpufreq: stats: don't update stats on false notifiers

We need to call cpufreq_stats_update() to update 'time_in_state' for the last
frequency. This is achieved by calling it from cpufreq_stat_notifier_trans(),
which is called after frequency transition.

But if we detect that the cpu's frequency haven't really changed and its a false
POSTCHANGE notification, we don't really need to update time_in_state.

It wouldn't cause any harm in calling cpufreq_stats_update() but we can avoid
calling it here and call it when the frequency really changes. The result will
be the same but more efficient.

Reviewed-by: Prarit Bhargava <[e-mail]>
Signed-off-by: Viresh Kumar <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/cpufreq/cpufreq_stats.c

···
 	if (old_index == -1 || new_index == -1)
 		goto put_policy;
 
-	cpufreq_stats_update(stats);
-
 	if (old_index == new_index)
 		goto put_policy;
+
+	cpufreq_stats_update(stats);
 
 	spin_lock(&cpufreq_stats_lock);
 	stats->last_index = new_index;