dt-bindings: ap806: add the cluster clock node in the syscon file

The Device Tree node representing the AP806 system controller provides

a number of clocks:

 - 0: clock of CPU cluster 0

 - 1: clock of CPU cluster 1

 - 0: reference clock of CPU cluster 0

 - 1: reference clock of CPU cluster 1

 - 2: fixed PLL at 1200 Mhz

 - 3: MSS clock, derived from the fixed PLL

		#thermal-sensor-cells = <1>;

	};

};

Cluster clocks:

---------------

Device Tree Clock bindings for cluster clock of AP806 Marvell. Each

cluster contain up to 2 CPUs running at the same frequency.

Required properties:

- compatible: must be  "marvell,ap806-cpu-clock";

- #clock-cells : should be set to 1.

- clocks : shall be the input parent clock(s) phandle for the clock

           (one per cluster)

- reg: register range associated with the cluster clocks

ap_syscon1: system-controller@6f8000 {

	compatible = "marvell,armada-ap806-syscon1", "syscon", "simple-mfd";

	reg = <0x6f8000 0x1000>;

	cpu_clk: clock-cpu@278 {

		compatible = "marvell,ap806-cpu-clock";

		clocks = <&ap_clk 0>, <&ap_clk 1>;

		#clock-cells = <1>;

		reg = <0x278 0xa30>;

	};

};