block: avoid creating invalid symlink file for patitions

hulk inclusion
category: bugfix
bugzilla: 55097
CVE: NA

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For now, there is no mechanism that can provent ioctl to call
add_partition after del_gendisk() have called delete_partition().
Then, invalid symlinks file may be created into /sys/class/block.

We try to fix this problem by setting GENHD_FL_UP early in del_gendisk()
and check the flag before adding partitions likely that do in
mainline kernel. Since all of them are cover by bdev->bd_mutex,
either add_partition success but will delete by del_gendisk(),
or add_partition will fail return as GENHD_FL_UP have been cleared.

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>