Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/csky/include/asm/bug.h b/arch/csky/include/asm/bug.h
new file mode 100644
index 0000000..bd7b323
--- /dev/null
+++ b/arch/csky/include/asm/bug.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
+
+#ifndef __ASM_CSKY_BUG_H
+#define __ASM_CSKY_BUG_H
+
+#include <linux/compiler.h>
+#include <linux/const.h>
+#include <linux/types.h>
+
+#define BUG()				\
+do {					\
+	asm volatile ("bkpt\n");	\
+	unreachable();			\
+} while (0)
+
+#define HAVE_ARCH_BUG
+
+#include <asm-generic/bug.h>
+
+struct pt_regs;
+
+void die_if_kernel(char *str, struct pt_regs *regs, int nr);
+void show_regs(struct pt_regs *regs);
+
+#endif /* __ASM_CSKY_BUG_H */