cpufreq: Move the IS_ENABLED(CPU_THERMAL) macro into a stub

cpufreq_online() and cpufreq_offline() [un]register the driver as
a cooling device. This is done if the driver is flagged as a cooling
device in addition with an IS_ENABLED() check to compile out the branching
code.

Group this test in a stub function added in the cpufreq header instead
of having the IS_ENABLED() in the code.
Suggested-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cpufreq.c

@@ -1378,8 +1378,7 @@ static int cpufreq_online(unsigned int cpu)
 	if (cpufreq_driver->ready)
 		cpufreq_driver->ready(policy);
 
-	if (IS_ENABLED(CONFIG_CPU_THERMAL) &&
-	    cpufreq_driver->flags & CPUFREQ_IS_COOLING_DEV)
+	if (cpufreq_thermal_control_enabled(cpufreq_driver))
 		policy->cdev = of_cpufreq_cooling_register(policy);
 
 	pr_debug("initialization complete\n");
@@ -1469,8 +1468,7 @@ static int cpufreq_offline(unsigned int cpu)
 		goto unlock;
 	}
 
-	if (IS_ENABLED(CONFIG_CPU_THERMAL) &&
-	    cpufreq_driver->flags & CPUFREQ_IS_COOLING_DEV) {
+	if (cpufreq_thermal_control_enabled(cpufreq_driver)) {
 		cpufreq_cooling_unregister(policy->cdev);
 		policy->cdev = NULL;
 	}

include/linux/cpufreq.h

@@ -409,6 +409,12 @@ int cpufreq_unregister_driver(struct cpufreq_driver *driver_data);
 const char *cpufreq_get_current_driver(void);
 void *cpufreq_get_driver_data(void);
 
+static inline int cpufreq_thermal_control_enabled(struct cpufreq_driver *drv)
+{
+	return IS_ENABLED(CONFIG_CPU_THERMAL) &&
+		(drv->flags & CPUFREQ_IS_COOLING_DEV);
+}
+
 static inline void cpufreq_verify_within_limits(struct cpufreq_policy *policy,
 		unsigned int min, unsigned int max)
 {