CVE-2024-56751 ipv6: release nexthop on device removal

In the Linux kernel, the following vulnerability has been resolved: ipv6: release nexthop on device removal The CI is hitting some aperiodic hangup at device removal time in the pmtu.sh self-test: unregisternetdevice: waiting for vethA-R1 to become free. Usage count = 6 reftracker:...