Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/mips/Kbuild.platforms b/arch/mips/Kbuild.platforms
index ac7ad54..0de8398 100644
--- a/arch/mips/Kbuild.platforms
+++ b/arch/mips/Kbuild.platforms
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0
 # All platforms listed in alphabetic order
 
 platforms += alchemy