Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/samples/configfs/Makefile b/samples/configfs/Makefile
index a9afd99..92d661f 100644
--- a/samples/configfs/Makefile
+++ b/samples/configfs/Makefile
@@ -1,2 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
 
 obj-$(CONFIG_SAMPLE_CONFIGFS) += configfs_sample.o