Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/init/version.c b/init/version.c
index ef4012e..cba3411 100644
--- a/init/version.c
+++ b/init/version.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *  linux/init/version.c
  *