block: Remove unused flush_queue_delayed in struct blk_flush_queue

The flush_queue_delayed was introdued to hold queue if flush is
running for non-queueable flush drive by commit 3ac0cc45
("hold queue if flush is running for non-queueable flush drive"),
but the non mq parts of the flush code had been removed by
commit 7e992f84 ("block: remove non mq parts from the flush code"),
as well as removing the usage of the flush_queue_delayed flag.
Thus remove the unused flush_queue_delayed flag.
Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-flush.c

@@ -258,7 +258,6 @@ static void flush_end_io(struct request *flush_rq, blk_status_t error)
 		blk_flush_complete_seq(rq, fq, seq, error);
 	}
 
-	fq->flush_queue_delayed = 0;
 	spin_unlock_irqrestore(&fq->mq_flush_lock, flags);
 }
 

block/blk.h

@@ -19,7 +19,6 @@ extern struct dentry *blk_debugfs_root;
 #endif
 
 struct blk_flush_queue {
-	unsigned int		flush_queue_delayed:1;
 	unsigned int		flush_pending_idx:1;
 	unsigned int		flush_running_idx:1;
 	blk_status_t 		rq_status;