blk-cgroup: fix missing put device in error path from blkg_conf_pref()

blk-cgroup: fix missing put device in error path from blkg_conf_pref()

If blk_queue_enter() failed due to queue is dying, the
blkdev_put_no_open() is needed because blkcg_conf_open_bdev() succeeded.

Fixes: 0c9d338c8443 ("blk-cgroup: synchronize blkg creation against policy deactivation")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20211102020705.2321858-1-yukuai3@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>