Rockchip NAND Flash Controller DT binding

Required properties:

- compatible : "rockchip,rk-nand-v9".
- 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 rk3326 / rkpx30:
	nandc0: nandc@ff3b0000 {
		compatible = "rockchip,rk-nandc-v9";
		reg = <0x0 0xff3b0000 0x0 0x4000>;
		interrupts = <GIC_SPI 57 IRQ_TYPE_LEVEL_HIGH>;
		nandc_id = <0>;
		clocks = <&cru SCLK_NANDC>, <&cru HCLK_NANDC>;
		clock-names = "clk_nandc", "hclk_nandc";
		assigned-clocks = <&cru SCLK_NANDC>;
		assigned-clock-parents = <&cru SCLK_NANDC_DIV50>;
		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>;
		};
	};