ARM: dts: rmobile: Add SoC and board U-Boot DT extras

Add U-Boot DT extras for each SoC and board. This marks the required
nodes with u-boot,dm-pre-reloc to start clock and PRR early on while
avoiding modification of the DTs imported from Linux.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/arch/arm/dts/r8a7794-u-boot.dtsi b/arch/arm/dts/r8a7794-u-boot.dtsi
new file mode 100644
index 0000000..e8bdcc9
--- /dev/null
+++ b/arch/arm/dts/r8a7794-u-boot.dtsi
@@ -0,0 +1,13 @@
+/*
+ * Device Tree Source extras for U-Boot on RCar R8A7794 SoC
+ *
+ * Copyright (C) 2018 Marek Vasut <marek.vasut@gmail.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0
+ */
+
+#include "r8a779x-u-boot.dtsi"
+
+&usb_extal_clk {
+	u-boot,dm-pre-reloc;
+};