seg6: fix the iif in the IPv6 socket control block
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 v4.19.221 by commit 6431e71093f3da586a00c6d931481ffb0dc2db0e, it was introduced in version v4.19.20 by commit 2f704348c93ff8119e642dae6a72327f90b82810. For more details please see the references link.