powerpc/kasan: Silence KASAN warnings in _getwchan()
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 v5.18.6 by commit 23f6ebb9717b5e1496e7cbed77736438f269a5e6. For more details please see the references link.