driver core: class: remove dev_kobj from struct class

The dev_kobj field in struct class is now only written to, but never
read from, so it can be removed as it is useless.

Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/20230331093318.82288-5-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

block/genhd.c

@@ -899,7 +899,6 @@ static int __init genhd_device_init(void)
 {
 	int error;
 
-	block_class.dev_kobj = sysfs_dev_block_kobj;
 	error = class_register(&block_class);
 	if (unlikely(error))
 		return error;