Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/net/switchdev/Kconfig b/net/switchdev/Kconfig
index 651fa20..50f21a6 100644
--- a/net/switchdev/Kconfig
+++ b/net/switchdev/Kconfig
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
 #
 # Configuration for Switch device support
 #