Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/mips/alchemy/common/Makefile b/arch/mips/alchemy/common/Makefile
index 23800b8..a0e9438 100644
--- a/arch/mips/alchemy/common/Makefile
+++ b/arch/mips/alchemy/common/Makefile
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
 #
 #  Copyright 2000, 2008 MontaVista Software Inc.
 #  Author: MontaVista Software, Inc. <source@mvista.com>