perf tests pmu: Add missing headers

It needs the definitions for PATH_MAX and snprintf, was getting it
by luck from headers it included and that are now being sanitized.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-7bbh3kk0h5mywvfqm64nhv28@git.kernel.org


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