dm: move setting md->type into dm_setup_md_queue

dm: move setting md->type into dm_setup_md_queue

Move setting md->type from both callers into dm_setup_md_queue.
This ensures that md->type is only set to a valid value after the queue
has been fully setup, something we'll rely on future changes.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Link: https://lore.kernel.org/r/20210804094147.459763-7-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>