block: stop setting the nomerges flags in blk_cleanup_queue

These flags only apply to file system I/O, and all file system I/O is
already drained by del_gendisk and thus can't be in progress when
blk_cleanup_queue is called.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20220619060552.1850436-5-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-core.c

@@ -304,9 +304,6 @@ void blk_cleanup_queue(struct request_queue *q)
 	blk_queue_flag_set(QUEUE_FLAG_DYING, q);
 	blk_queue_start_drain(q);
 
-	blk_queue_flag_set(QUEUE_FLAG_NOMERGES, q);
-	blk_queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
-
 	/*
 	 * Drain all requests queued before DYING marking. Set DEAD flag to
 	 * prevent that blk_mq_run_hw_queues() accesses the hardware queues