ublk_drv: return flag of UBLK_F_URING_CMD_COMP_IN_TASK in case of module

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: 71f28f3136af ("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>