Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/drivers/net/ethernet/dec/Makefile b/drivers/net/ethernet/dec/Makefile
index 32993fc..e8aa12c 100644
--- a/drivers/net/ethernet/dec/Makefile
+++ b/drivers/net/ethernet/dec/Makefile
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
 #
 # Makefile for the Digital Equipment Inc. network device drivers.
 #