block: fix debugfs config conditional in struct request_queue

The debugfs dentries are only used for CONFIG_BLK_DEBUG_FS, so make them
conditional on that instead of CONFIG_DEBUG_FS.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

include/linux/blkdev.h

@@ -570,7 +570,7 @@ struct request_queue {
 	struct list_head	tag_set_list;
 	struct bio_set		*bio_split;
 
-#ifdef CONFIG_DEBUG_FS
+#ifdef CONFIG_BLK_DEBUG_FS
 	struct dentry		*debugfs_dir;
 	struct dentry		*mq_debugfs_dir;
 #endif