Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/drivers/ide/cmd640.c b/drivers/ide/cmd640.c
index 004243b..f48decb 100644
--- a/drivers/ide/cmd640.c
+++ b/drivers/ide/cmd640.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *  Copyright (C) 1995-1996  Linus Torvalds & authors (see below)
  */