Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/csky/include/asm/vdso.h b/arch/csky/include/asm/vdso.h
new file mode 100644
index 0000000..d963d69
--- /dev/null
+++ b/arch/csky/include/asm/vdso.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __ASM_CSKY_VDSO_H
+#define __ASM_CSKY_VDSO_H
+
+#include <abi/vdso.h>
+
+struct csky_vdso {
+	unsigned short rt_signal_retcode[4];
+};
+
+#endif /* __ASM_CSKY_VDSO_H */