cpufreq: move to use bus_get_dev_root()

Direct access to the struct bus_type dev_root pointer is going away soon
so replace that with a call to bus_get_dev_root() instead, which is what
it is there for.

Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: linux-pm@vger.kernel.org
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20230313182918.1312597-3-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/cpufreq/cpufreq.c

@@ -2932,11 +2932,16 @@ EXPORT_SYMBOL_GPL(cpufreq_unregister_driver);
 static int __init cpufreq_core_init(void)
 {
 	struct cpufreq_governor *gov = cpufreq_default_governor();
+	struct device *dev_root;
 
 	if (cpufreq_disabled())
 		return -ENODEV;
 
-	cpufreq_global_kobject = kobject_create_and_add("cpufreq", &cpu_subsys.dev_root->kobj);
+	dev_root = bus_get_dev_root(&cpu_subsys);
+	if (dev_root) {
+		cpufreq_global_kobject = kobject_create_and_add("cpufreq", &dev_root->kobj);
+		put_device(dev_root);
+	}
 	BUG_ON(!cpufreq_global_kobject);
 
 	if (!strlen(default_governor))

drivers/cpufreq/intel_pstate.c

@@ -1473,10 +1473,13 @@ static struct kobject *intel_pstate_kobject;
 
 static void __init intel_pstate_sysfs_expose_params(void)
 {
+	struct device *dev_root = bus_get_dev_root(&cpu_subsys);
 	int rc;
 
-	intel_pstate_kobject = kobject_create_and_add("intel_pstate",
-						&cpu_subsys.dev_root->kobj);
+	if (dev_root) {
+		intel_pstate_kobject = kobject_create_and_add("intel_pstate", &dev_root->kobj);
+		put_device(dev_root);
+	}
 	if (WARN_ON(!intel_pstate_kobject))
 		return;