ublk_drv: don't probe partitions if the ubq daemon isn't trusted

ublk_drv: don't probe partitions if the ubq daemon isn't trusted

If any ubq daemon is unprivileged, the ublk char device is allowed
for unprivileged user actually, and we can't trust the current user,
so not probe partitions.

Fixes: 71f28f3136af ("ublk_drv: add io_uring based userspace block driver")
Reviewed-by: ZiyangZhang <ZiyangZhang@linux.alibaba.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230106041711.914434-3-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>