Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/csky/include/asm/cacheflush.h b/arch/csky/include/asm/cacheflush.h
new file mode 100644
index 0000000..a96da67
--- /dev/null
+++ b/arch/csky/include/asm/cacheflush.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
+
+#ifndef __ASM_CSKY_CACHEFLUSH_H
+#define __ASM_CSKY_CACHEFLUSH_H
+
+#include <abi/cacheflush.h>
+
+#endif /* __ASM_CSKY_CACHEFLUSH_H */