CVE-2022-49955 powerpc/rtas: Fix RTAS MSR[HV] handling for Cell

In the Linux kernel, the following vulnerability has been resolved: powerpc/rtas: Fix RTAS MSRHV handling for Cell The semi-recent changes to MSR handling when entering RTAS firmware cause crashes on IBM Cell machines. An example trace: kernel tried to execute user page 2fff01a8 - exploit attempt...