Driver Core: do not oops when driver_unregister() is called for unregistered drivers

We also fix a problem with cleaning up properly when initializing
drivers and devices, so checks like this will work successfully.

Portions of the patch by Linus and Greg and Ingo.

Reported-by: Ozan Çağlayan <ozan@pardus.org.tr>
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/base/bus.c

@@ -700,8 +700,10 @@ int bus_add_driver(struct device_driver *drv)
 	}
 
 	kobject_uevent(&priv->kobj, KOBJ_ADD);
-	return error;
+	return 0;
 out_unregister:
+	kfree(drv->p);
+	drv->p = NULL;
 	kobject_put(&priv->kobj);
 out_put_bus:
 	bus_put(bus);