ublk_drv: return flag of UBLK_F_URING_CMD_COMP_IN_TASK in case of module

UBLK_F_URING_CMD_COMP_IN_TASK needs to be set and returned to userspace
if ublk driver is built as module, otherwise userspace may get wrong
flags shown.

Fixes: 71f28f3 ("ublk_drv: add io_uring based userspace block driver")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: ZiyangZhang <ZiyangZhang@linux.alibaba.com>
Link: https://lore.kernel.org/r/20221029010432.598367-2-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Ming Lei

drivers/block/ublk_drv.c

@@ -1658,6 +1658,9 @@ static int ublk_ctrl_add_dev(struct io_uring_cmd *cmd)
 	 */
 	ub->dev_info.flags &= UBLK_F_ALL;
 
+	if (!IS_BUILTIN(CONFIG_BLK_DEV_UBLK))
+		ub->dev_info.flags |= UBLK_F_URING_CMD_COMP_IN_TASK;
+
 	/* We are not ready to support zero copy */
 	ub->dev_info.flags &= ~UBLK_F_SUPPORT_ZERO_COPY;