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 v5.10.124 by commit 2c9548bc2650b3a2778050f62d8f683f507e6e6d. For more details please see the references link.