CVE-2025-38233 powerpc64/ftrace: fix clobbered r15 during livepatching

In the Linux kernel, the following vulnerability has been resolved: powerpc64/ftrace: fix clobbered r15 during livepatching While r15 is clobbered always with PPCFTRACEOUTOFLINE, it is not restored in livepatch sequence leading to not so obvious fails like below: BUG: Unable to handle kernel data...