nbd: fix possible overflow on 'firstminor' in nbddev_add()
This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v5.15.34 by commit 5142720dbe51befeb25f204f912ef1ad93fba343, it was introduced in version v4.11 by commit b0d9111a2d53785847763c64c40af2d4c4c5a8b7. For more details please see the references link.