CVE-2026-64452 6lowpan: fix NHC entry use-after-free on error path

In the Linux kernel, the following vulnerability has been resolved: 6lowpan: fix NHC entry use-after-free on error path lowpannhcdouncompression looks up an NHC descriptor while holding lowpannhclock. If the descriptor has no uncompress callback, the error path drops the lock before printing...