ARM: dts: renesas: Add R8A779A0 V3U DT extras

Add R8A779A0 V3U DT extras for U-Boot.

Based on "ARM: dts: renesas: Add R8A779A0 V3U DTs"
by Hai Pham <hai.pham.ud@renesas.com>

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>

arch/arm/dts/r8a779a0-u-boot.dtsi

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Device Tree Source extras for U-Boot on R-Car R8A779A0 SoC
+ *
+ * Copyright (C) 2020 Renesas Electronics Corp.
+ */
+
+#include "r8a779x-u-boot.dtsi"
+
+&extalr_clk {
+	u-boot,dm-pre-reloc;
+};