driver core: class: remove subsystem private pointer from struct class

Now that the last users of the subsystem private pointer in struct class
are gone, the pointer can be removed, as no one is using it.  One step
closer to allowing struct class to be const and moved into read-only
memory.
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/20230331093318.82288-3-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/class.c

@@ -97,8 +97,6 @@ static void class_release(struct kobject *kobj)
 
 	pr_debug("class '%s': release.\n", class->name);
 
-	class->p = NULL;
-
 	if (class->class_release)
 		class->class_release(class);
 	else
@@ -206,7 +204,6 @@ int class_register(struct class *cls)
 	cp->subsys.kobj.kset = class_kset;
 	cp->subsys.kobj.ktype = &class_ktype;
 	cp->class = cls;
-	cls->p = cp;
 
 	error = kset_register(&cp->subsys);
 	if (error)
@@ -222,7 +219,6 @@ int class_register(struct class *cls)
 
 err_out:
 	kfree(cp);
-	cls->p = NULL;
 	return error;
 }
 EXPORT_SYMBOL_GPL(class_register);

include/linux/device/class.h

@@ -71,8 +71,6 @@ struct class {
 	void (*get_ownership)(const struct device *dev, kuid_t *uid, kgid_t *gid);
 
 	const struct dev_pm_ops *pm;
-
-	struct subsys_private *p;
 };
 
 struct class_dev_iter {