thermal: core: Introduce thermal_cooling_device_present()

Introduce a helper function, thermal_cooling_device_present(), for
checking if the given cooling device is in the list of registered
cooling devices to avoid some code duplication in a subsequent
patch.

No expected functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Zhang Rui <rui.zhang@intel.com>
Reviewed-by: Zhang Rui <rui.zhang@intel.com>
Acked-by: Nathan Hartman <nhartman@nvidia.com>
Acked-by: Jamie Nguyen <jamien@nvidia.com>

Author: rafaeljw

drivers/thermal/thermal_core.c

@@ -1052,6 +1052,18 @@ devm_thermal_of_cooling_device_register(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(devm_thermal_of_cooling_device_register);
 
+static bool thermal_cooling_device_present(struct thermal_cooling_device *cdev)
+{
+	struct thermal_cooling_device *pos = NULL;
+
+	list_for_each_entry(pos, &thermal_cdev_list, node) {
+		if (pos == cdev)
+			return true;
+	}
+
+	return false;
+}
+
 static void __unbind(struct thermal_zone_device *tz, int mask,
 		     struct thermal_cooling_device *cdev)
 {
@@ -1074,20 +1086,17 @@ void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev)
 	int i;
 	const struct thermal_zone_params *tzp;
 	struct thermal_zone_device *tz;
-	struct thermal_cooling_device *pos = NULL;
 
 	if (!cdev)
 		return;
 
 	mutex_lock(&thermal_list_lock);
-	list_for_each_entry(pos, &thermal_cdev_list, node)
-		if (pos == cdev)
-			break;
-	if (pos != cdev) {
-		/* thermal cooling device not found */
+
+	if (!thermal_cooling_device_present(cdev)) {
 		mutex_unlock(&thermal_list_lock);
 		return;
 	}
+
 	list_del(&cdev->node);
 
 	/* Unbind all thermal zones associated with 'this' cdev */