perf tools: Fix buffer allocation

"perf top" cores dump on my dev machine, if run from a directory
where vmlinux is present:

  *** glibc detected *** malloc(): memory corruption: 0x085670d0 ***
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Cc: <stable@kernel.org>
LKML-Reference: <4ABB6EB7.7000002@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

tools/perf/util/module.c

@@ -423,7 +423,7 @@ static int mod_dso__load_module_paths(struct mod_dso *self)
 	len += strlen(uts.release);
 	len += strlen("/modules.dep");
 
-	dpath = calloc(1, len);
+	dpath = calloc(1, len + 1);
 	if (dpath == NULL)
 		return err;