Rockchip NAND Flash Controller DT binding

Required properties:

- compatible : "rockchip,rk-nand".
- reg : shall contain registers location and length for data and reg.
- interrupts : shall define the nand controller interrupt.
- clocks : shall reference nand controller clocks.
- clock-names : nand controller internal clock names. Shall contain :
    * "hclk_nandc" : AHB gating clock
    * "clk_nandc" : nand controller clock

Example for rk322x:
	nandc: nandc@10500000 {
		compatible = "rockchip,rk-nand";
		reg = <0x10500000 0x4000>;
		interrupts = <GIC_SPI 18 IRQ_TYPE_LEVEL_HIGH>;
		clocks = <&clk_nandc>, <&clk_gates10 15>;
		clock-names = "clk_nandc", "hclk_nandc";
		clock-frequency = <150000000>;
		status = "okay";

		#address-cells = <1>;
		#size-cells = <1>;
		nand@0 {
			reg = <0>;
			nand-ecc-mode = "hw";
			nand-ecc-strength = <16>;
			nand-ecc-step-size = <1024>;
		};
	};