ARM: kirkwood: add i2c-gpio controller for km_kirkwood

This controller is used to access the reset management FPGA of the
km_kirkwood boards.
Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

arch/arm/boot/dts/kirkwood-km_kirkwood.dts

@@ -42,4 +42,11 @@ nand@3000000 {
 			chip-delay = <25>;
 		};
 	};
+
+	i2c@0 {
+		compatible = "i2c-gpio";
+		gpios = < &gpio0 8 0		/* sda */
+			&gpio0 9 0 >;		/* scl */
+		i2c-gpio,delay-us = <2>;	/* ~100 kHz */
+	};
 };