ublk: improve getting & putting ublk device

ublk: improve getting & putting ublk device

Firstly convert get_device() and put_device() into ublk_get_device()
and ublk_put_device().

Secondly annotate ublk_get_device() & ublk_put_device() as noinline
for trace, especially it is often to trigger device deletion hang
when incorrect order is used on ublkc mmap, ublkc close,
io_uring_sqe_unregister_file, ublkb close.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20240223075539.89945-2-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>