ublk: move ublk_cancel_dev() out of ub->mutex

ublk: move ublk_cancel_dev() out of ub->mutex

ublk_cancel_dev() just calls ublk_cancel_queue() to cancel all pending
io commands after ublk request queue is idle. The only protection is just
the read & write of ubq->nr_io_ready and avoid duplicated command cancel,
so add one per-queue lock with cancel flag for providing this protection,
meantime move ublk_cancel_dev() out of ub->mutex.

Then we needn't to call io_uring_cmd_complete_in_task() to cancel
pending command. And the same cancel logic will be re-used for
cancelable uring command.

This patch basically reverts commit ac5902f84bb5 ("ublk: fix AB-BA lockdep warning").

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20231009093324.957829-4-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>