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>

tools/perf/tests/pmu.c

@@ -4,7 +4,9 @@
 #include "util.h"
 #include "tests.h"
 #include <errno.h>
+#include <stdio.h>
 #include <linux/kernel.h>
+#include <linux/limits.h>
 
 /* Simulated format definitions. */
 static struct test_format {