block: fix that part scan is disabled in device_add_disk()

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5ETAB


CVE: NA

--------------------------------

Patch ("block: Fix warning in bd_link_disk_holder()") moves the
setting of flag 'GENHD_FL_UP' behind blkdev_get, which will
disabled part scan:

devcie_add_disk
 register_disk
  blkdev_get
   __blkdev_get
    bdev_get_gendisk
     get_gendisk -> failed because 'GENHD_FL_UP' is not set

And this will cause tests block/017, block/018 and scsi/004 to fail.

Fix the problem by moving part scan as well.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>