nbd: Reorganize the messy commit log about the first_minor check

hulk inclusion
category: bugfix
bugzilla: 188217

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Commits on our branch with check issues on first_minor had serious
confusion, resulting in duplicate checks in nbd_dev_add and
nbd_genl_connect.

So I revert the messy commit, backport lts patch.

Revert 84c282c6
  ("nbd: fix possible overflow for 'first_minor' in nbd_dev_add()")
Revert 39a42d5e ("nbd: fix max value for 'first_minor'")
Revert 3ddba49a
  ("Revert "Revert "block: nbd: add sanity check for first_minor""")
Revert 3bb2913d
  ("nbd: fix assignment error for first_minor in nbd_dev_add")
Revert 648bb72a
  ("nbd: fix possible overflow on 'first_minor' in nbd_dev_add()")
Revert 60141517 ("nbd: Fix use-after-free in blk_mq_free_rqs")
Revert 98d3ad1d ("nbd: add sanity check for first_minor")

Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com>
Signed-off-by: Li Nan <linan122@huawei.com>