perf test: Skip wp modify test on old kernels

It uses PERF_EVENT_IOC_MODIFY_ATTRIBUTES ioctl.	 The kernel would return
ENOTTY if it's not supported.  Update the skip reason in that case.

Committer notes:

On s/390 the args aren't used, so need to be marked __maybe_unused.

Reviewed-by: Ravi Bangoria <ravi.bangoria@amd.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lore.kernel.org/r/20220914183338.546357-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>