arm64: dts: renesas: spider: Add Ethernet sub-board

Add a DTS file for the Spider Ether TSN sub-board (RTP8A779F0ASKB0ST0S),
and include it from the main r8a779f0-spider.dts.

For now its contents are limited to the Board ID EEPROM.

Extracted from a larger patch in the BSP by LUU HOAI.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/5aa58816182b34d9e5795bc1e22784f4e4879d13.1643898884.git.geert+renesas@glider.be

arch/arm64/boot/dts/renesas/r8a779f0-spider-ethernet.dtsi

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Device Tree Source for the Spider Ethernet sub-board
+ *
+ * Copyright (C) 2021 Renesas Electronics Corp.
+ */
+
+&i2c4 {
+	eeprom@52 {
+		compatible = "rohm,br24g01", "atmel,24c01";
+		label = "ethernet-sub-board";
+		reg = <0x52>;
+		pagesize = <8>;
+	};
+};

arch/arm64/boot/dts/renesas/r8a779f0-spider.dts

@@ -7,6 +7,7 @@
 
 /dts-v1/;
 #include "r8a779f0-spider-cpu.dtsi"
+#include "r8a779f0-spider-ethernet.dtsi"
 
 / {
 	model = "Renesas Spider CPU and Breakout boards based on r8a779f0";