dm: cleanup cleanup_mapped_device

md->queue is now always set when md->disk is set, so simplify the
conditionals a bit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Link: https://lore.kernel.org/r/20210804094147.459763-6-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>