CVE-2026-90272 perf: arm_pmuv3: Zero initialize hw_id branch stack field

In the Linux kernel, the following vulnerability has been resolved: perf: armpmuv3: Zero initialize hwid branch stack field PERFSAMPLEBRANCHHWINDEX is supported by BRBE so hwid is passed to userspace, but it's never set by the BRBE driver. Zero initialize it as it should be according to the docs:...