kgdboc: fix return value of __setup handler
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 v4.19.238 by commit 1c3bb588b78e07f97e5a55fb523d103d124050a1, it was introduced in version v4.19.2 by commit df7ada33d6dc57926e25e4cf1a22e80b4f385884. For more details please see the references link.