tools lib: Adopt zalloc()/zfree() from tools/perf

Eroding a bit more the tools/perf/util/util.h hodpodge header.

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-natazosyn9rwjka25tvcnyi0@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/builtin-help.c b/tools/perf/builtin-help.c
index 6a1cab5..a83af92 100644
--- a/tools/perf/builtin-help.c
+++ b/tools/perf/builtin-help.c
@@ -14,6 +14,7 @@
 #include <subcmd/help.h>
 #include "util/debug.h"
 #include <linux/kernel.h>
+#include <linux/zalloc.h>
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>