Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/sh/mm/kmap.c b/arch/sh/mm/kmap.c
index bf25d7c..9e6b38b 100644
--- a/arch/sh/mm/kmap.c
+++ b/arch/sh/mm/kmap.c
@@ -1,10 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * arch/sh/mm/kmap.c
  *
  * Copyright (C) 1999, 2000, 2002  Niibe Yutaka
  * Copyright (C) 2002 - 2009  Paul Mundt
- *
- * Released under the terms of the GNU GPL v2.0.
  */
 #include <linux/mm.h>
 #include <linux/init.h>