ARM: dts: marzen: Enable I2C support

Enable the single I2C bus available on the Marzen development board.
As this bus contains an AK4643 codec, it must be limited to 100 kHz.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/77b87378397fd26f39c73f68e3ea465db6d38fb1.1679330016.git.geert+renesas@glider.be

arch/arm/boot/dts/r8a7779-marzen.dts

@@ -215,6 +215,12 @@ keyboard-irq-hog {
 	};
 };
 
+&i2c0 {
+	status = "okay";
+
+	clock-frequency = <100000>;
+};
+
 &irqpin0 {
 	status = "okay";
 };