nbd: Revert redundant patches of nbd first_minor

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I81XCK



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

After commit 648bb72a ("nbd: fix possible overflow on 'first_minor' in
nbd_dev_add()"), the issue of nbd first_minor has been completely
resolved. Therefore, revert the redundant patches after this commit.

Revert "nbd: fix possible overflow for 'first_minor' in nbd_dev_add()"
This reverts commit e7155946.

Revert "nbd: fix max value for 'first_minor'"
This reverts commit 3d2fe8ed.

Revert "Revert "Revert "block: nbd: add sanity check for first_minor"""
This reverts commit 6081b563.

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