perf beauty: Update the linux/perf_event.h copy with the kernel sources

Update it as one comment got realigned, probably in a merge, so no
changes in perf tooling, just silences this build warning:

  Warning: Kernel ABI header differences:
    diff -u tools/include/uapi/linux/perf_event.h include/uapi/linux/perf_event.h

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>