Having this in Yama would also make it probable that there would be a
security-centric default. It would end up wiping out unprivileged perf
events access on distributions using Yama for ptrace_scope unless they
make the explicit decision to disable it. Having the perf subsystem
extend the existing perf_event_paranoid sysctl leaves the control over
the upstream default in the hands of the perf subsystem, not LSMs.