Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/drivers/net/ethernet/apm/Kconfig b/drivers/net/ethernet/apm/Kconfig
index 59efe5b..a893ef0 100644
--- a/drivers/net/ethernet/apm/Kconfig
+++ b/drivers/net/ethernet/apm/Kconfig
@@ -1,2 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
 source "drivers/net/ethernet/apm/xgene/Kconfig"
 source "drivers/net/ethernet/apm/xgene-v2/Kconfig"