ublk: move device reset into ublk_ch_release()

ublk: move device reset into ublk_ch_release()

ublk_ch_release() is called after ublk char device is closed, when all
uring_cmd are done, so it is perfect fine to move ublk device reset to
ublk_ch_release() from ublk_ctrl_start_recovery().

This way can avoid to grab the exiting daemon task_struct too long.

However, reset of the following ublk IO flags has to be moved until ublk
io_uring queues are ready:

- ubq->canceling

For requeuing IO in case of ublk_nosrv_dev_should_queue_io() before device
is recovered

- ubq->fail_io

For failing IO in case of UBLK_F_USER_RECOVERY_FAIL_IO before device is
recovered

- ublk_io->flags

For preventing using io->cmd

With this way, recovery is simplified a lot.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250416035444.99569-5-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>