Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/tools/spi/Makefile b/tools/spi/Makefile
index 815d155..5c342e6 100644
--- a/tools/spi/Makefile
+++ b/tools/spi/Makefile
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
 include ../scripts/Makefile.include
 
 bindir ?= /usr/bin