Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/tools/perf/util/help-unknown-cmd.c b/tools/perf/util/help-unknown-cmd.c
index 4f07a5b..ab9e161 100644
--- a/tools/perf/util/help-unknown-cmd.c
+++ b/tools/perf/util/help-unknown-cmd.c
@@ -3,9 +3,11 @@
 #include "config.h"
 #include <poll.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <subcmd/help.h>
 #include "../builtin.h"
 #include "levenshtein.h"
+#include <linux/zalloc.h>
 
 static int autocorrect;