Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/drivers/net/plip/Kconfig b/drivers/net/plip/Kconfig
index 80c4a33..b41035b 100644
--- a/drivers/net/plip/Kconfig
+++ b/drivers/net/plip/Kconfig
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
 #
 # Parallel Line Internet Protocol (PLIP) network device configuration
 #