sysdev: fix problem with sysdev_class being re-registered

We need to initialize the kobject for a sysdev_class as it could have
been recycled (stupid static kobjects...)

We also do the same thing in case sysdev devices are being
re-registered.

Thanks to Balaji Rao <[e-mail]> for pointing out the
problem.

Signed-off-by: Balaji Rao <[e-mail]>
Tested-by: Mikael Pettersson <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/base/sys.c

···
 	pr_debug("Registering sysdev class '%s'\n",
 		 kobject_name(&cls->kset.kobj));
 	INIT_LIST_HEAD(&cls->drivers);
+	memset(&cls->kset.kobj, 0x00, sizeof(struct kobject));
 	cls->kset.kobj.parent = &system_kset->kobj;
 	cls->kset.kobj.ktype = &ktype_sysdev_class;
 	cls->kset.kobj.kset = system_kset;
···
 		return -EINVAL;
 
 	pr_debug("Registering sys device '%s'\n", kobject_name(&sysdev->kobj));
+
+	/* initialize the kobject to 0, in case it had previously been used */
+	memset(&sysdev->kobj, 0x00, sizeof(struct kobject));
 
 	/* Make sure the kset is set */
 	sysdev->kobj.kset = &cls->kset;