platform/x86: intel-uncore-freq: 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: Mark Gross <markgross@kernel.org>
Cc: platform-driver-x86@vger.kernel.org
Acked-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Link: https://lore.kernel.org/r/20230313182918.1312597-5-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/platform/x86/intel/uncore-frequency/uncore-frequency-common.c

@@ -224,9 +224,15 @@ int uncore_freq_common_init(int (*read_control_freq)(struct uncore_data *data, u
 	uncore_write = write_control_freq;
 	uncore_read_freq = read_freq;
 
-	if (!uncore_root_kobj)
-		uncore_root_kobj = kobject_create_and_add("intel_uncore_frequency",
-							    &cpu_subsys.dev_root->kobj);
+	if (!uncore_root_kobj) {
+		struct device *dev_root = bus_get_dev_root(&cpu_subsys);
+
+		if (dev_root) {
+			uncore_root_kobj = kobject_create_and_add("intel_uncore_frequency",
+								  &dev_root->kobj);
+			put_device(dev_root);
+		}
+	}
 	if (uncore_root_kobj)
 		++uncore_instance_count;
 	mutex_unlock(&uncore_lock);