Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/sh/kernel/kgdb.c b/arch/sh/kernel/kgdb.c
index 4f04c66..6d61f8c 100644
--- a/arch/sh/kernel/kgdb.c
+++ b/arch/sh/kernel/kgdb.c
@@ -1,13 +1,10 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * SuperH KGDB support
  *
  * Copyright (C) 2008 - 2012  Paul Mundt
  *
  * Single stepping taken from the old stub by Henry Bell and Jeremy Siegel.
- *
- * This file is subject to the terms and conditions of the GNU General Public
- * License.  See the file "COPYING" in the main directory of this archive
- * for more details.
  */
 #include <linux/kgdb.h>
 #include <linux/kdebug.h>
@@ -314,18 +311,6 @@
 	local_irq_restore(flags);
 }
 
-static void kgdb_call_nmi_hook(void *ignored)
-{
-	kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
-}
-
-void kgdb_roundup_cpus(unsigned long flags)
-{
-	local_irq_enable();
-	smp_call_function(kgdb_call_nmi_hook, NULL, 0);
-	local_irq_disable();
-}
-
 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
 {
 	int ret;
@@ -382,7 +367,7 @@
 	unregister_die_notifier(&kgdb_notifier);
 }
 
-struct kgdb_arch arch_kgdb_ops = {
+const struct kgdb_arch arch_kgdb_ops = {
 	/* Breakpoint instruction: trapa #0x3c */
 #ifdef CONFIG_CPU_LITTLE_ENDIAN
 	.gdb_bpt_instr		= { 0x3c, 0xc3 },