cpufreq: Use static SRCU initializer

Use the static SRCU initializer for `cpufreq_transition_notifier_list'.
This avoids the init_cpufreq_transition_notifier_list() initcall. Its
only purpose is to initialize the SRCU notifier once during boot and set
another variable which is used as an indicator whether the init was
perfromed before cpufreq_register_notifier() was used.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cpufreq.c

@@ -89,16 +89,7 @@ static void cpufreq_governor_limits(struct cpufreq_policy *policy);
  * The mutex locks both lists.
  */
 static BLOCKING_NOTIFIER_HEAD(cpufreq_policy_notifier_list);
-static struct srcu_notifier_head cpufreq_transition_notifier_list;
-
-static bool init_cpufreq_transition_notifier_list_called;
-static int __init init_cpufreq_transition_notifier_list(void)
-{
-	srcu_init_notifier_head(&cpufreq_transition_notifier_list);
-	init_cpufreq_transition_notifier_list_called = true;
-	return 0;
-}
-pure_initcall(init_cpufreq_transition_notifier_list);
+SRCU_NOTIFIER_HEAD_STATIC(cpufreq_transition_notifier_list);
 
 static int off __read_mostly;
 static int cpufreq_disabled(void)
@@ -1767,8 +1758,6 @@ int cpufreq_register_notifier(struct notifier_block *nb, unsigned int list)
 	if (cpufreq_disabled())
 		return -EINVAL;
 
-	WARN_ON(!init_cpufreq_transition_notifier_list_called);
-
 	switch (list) {
 	case CPUFREQ_TRANSITION_NOTIFIER:
 		mutex_lock(&cpufreq_fast_switch_lock);