ublk: fix error code for unsupported command

ENOTSUPP is for kernel use only, and shouldn't be sent to userspace.

Fix it by replacing it with EOPNOTSUPP.

Cc: stable@vger.kernel.org
Fixes: bfbcef03 ("ublk_drv: move ublk_get_device_from_id into ublk_ctrl_uring_cmd")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20241119030646.2319030-1-ming.lei@redhat.com


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