Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/mips/loongson64/common/reset.c b/arch/mips/loongson64/common/reset.c
index a60715e..ce39e91 100644
--- a/arch/mips/loongson64/common/reset.c
+++ b/arch/mips/loongson64/common/reset.c
@@ -1,8 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
- * This program is free software; you can redistribute	it and/or modify it
- * under  the terms of	the GNU General	 Public License as published by the
- * Free Software Foundation;  either version 2 of the  License, or (at your
- * option) any later version.
  *
  * Copyright (C) 2007 Lemote, Inc. & Institute of Computing Technology
  * Author: Fuxin Zhang, zhangfx@lemote.com
@@ -59,7 +56,12 @@
 {
 #ifndef CONFIG_LEFI_FIRMWARE_INTERFACE
 	mach_prepare_shutdown();
-	unreachable();
+
+	/*
+	 * It needs a wait loop here, but mips/kernel/reset.c already calls
+	 * a generic delay loop, machine_hang(), so simply return.
+	 */
+	return;
 #else
 	void (*fw_poweroff)(void) = (void *)loongson_sysconf.poweroff_addr;