block: fix inconsistent parenthesisation of QUEUE_FLAG_DEFAULT

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

include/linux/blkdev.h

@@ -455,7 +455,7 @@ struct request_queue
 
 #define QUEUE_FLAG_DEFAULT	((1 << QUEUE_FLAG_IO_STAT) |		\
 				 (1 << QUEUE_FLAG_CLUSTER) |		\
-				  1 << QUEUE_FLAG_STACKABLE)
+				 (1 << QUEUE_FLAG_STACKABLE))
 
 static inline int queue_is_locked(struct request_queue *q)
 {