driver core: change to_subsys_private() to use container_of_const()

The macro to_subsys_private() needs to switch to using
container_of_const() as it turned out to being incorrectly casting a
const pointer to a non-const one.  Make this change and fix up the one
offending user to be correctly handling a const pointer properly.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Reviewed-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20230111093327.3955063-1-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/base.h

@@ -53,7 +53,7 @@ struct subsys_private {
 	struct kset glue_dirs;
 	struct class *class;
 };
-#define to_subsys_private(obj) container_of(obj, struct subsys_private, subsys.kobj)
+#define to_subsys_private(obj) container_of_const(obj, struct subsys_private, subsys.kobj)
 
 struct driver_private {
 	struct kobject kobj;

drivers/base/class.c

@@ -64,7 +64,7 @@ static void class_release(struct kobject *kobj)
 
 static const struct kobj_ns_type_operations *class_child_ns_type(const struct kobject *kobj)
 {
-	struct subsys_private *cp = to_subsys_private(kobj);
+	const struct subsys_private *cp = to_subsys_private(kobj);
 	struct class *class = cp->class;
 
 	return class->ns_type;