Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/x86/lib/cmdline.c b/arch/x86/lib/cmdline.c
index 3261abb..4f1719e 100644
--- a/arch/x86/lib/cmdline.c
+++ b/arch/x86/lib/cmdline.c
@@ -1,6 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
- * This file is part of the Linux kernel, and is made available under
- * the terms of the GNU General Public License version 2.
  *
  * Misc librarized functions for cmdline poking.
  */