ARM: Kirkwood: Add missing DT reg property to cpu@0

The kirkwood.dtsi cpu@0 node is missing the mandatory reg property.
This causes of_get_cpu_node() to fail to find the node and as a result
the cpufreq driver fails in its probe function.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

arch/arm/boot/dts/kirkwood.dtsi

@@ -13,6 +13,7 @@ cpus {
 		cpu@0 {
 			device_type = "cpu";
 			compatible = "marvell,feroceon";
+			reg = <0>;
 			clocks = <&core_clk 1>, <&core_clk 3>, <&gate_clk 11>;
 			clock-names = "cpu_clk", "ddrclk", "powersave";
 		};