genhd must_check warning fix

Fixes:

block/genhd.c:361: warning: ignoring return value of ‘class_register’, declared with attribute warn_unused_result

Signed-off-by: Roland McGrath <[e-mail]>
Acked-by: Jeff Garzik <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

block/genhd.c

···
 
 static int __init genhd_device_init(void)
 {
-	class_register(&block_class);
+	int error = class_register(&block_class);
+	if (unlikely(error))
+		return error;
 	bdev_map = kobj_map_init(base_probe, &block_class_lock);
 	blk_dev_init();