net: fix UaF in netns ops registration error path
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 v5.15.91 by commit 66689a72ba73575e76d4f6a8748d3fa2690ec1c4, it was introduced in version v5.15.77 by commit a1e18acb0246bfb001b08b8b1b830b5ec92a0f13. For more details please see the references link.