mISDN: fix possible use-after-free in HFC_cleanup()
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 v4.14.240 by commit 7867ddc5f3de7f289aee63233afc0df4b62834c5. For more details please see the references link.