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 v4.19.198 by commit 5f2818185da0fe82a932f0856633038b66faf124. For more details please see the references link.