block: move blk_mq_add_queue_tag_set() after blk_mq_map_swqueue()

block: move blk_mq_add_queue_tag_set() after blk_mq_map_swqueue()

Move blk_mq_add_queue_tag_set() after blk_mq_map_swqueue(), and publish
this request queue to tagset after everything is setup.

This way is safe because BLK_MQ_F_TAG_QUEUE_SHARED isn't used by
blk_mq_map_swqueue(), and this flag is mainly checked in fast IO code
path.

Prepare for removing ->elevator_lock from blk_mq_map_swqueue() which
is supposed to be called when elevator switch can't be done.

Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reported-by: Nilay Shroff <nilay@linux.ibm.com>
Closes: https://lore.kernel.org/linux-block/567cb7ab-23d6-4cee-a915-c8cdac903ddd@linux.ibm.com/
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250505141805.2751237-2-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>