* Rockchip Audio PWM controller

Required properties:

- compatible: "rockchip,audio-pwm-v1"
- reg: physical base address of the controller and length of memory mapped
  region.
- dmas: DMA specifiers for tx dma. See the DMA client binding,
	Documentation/devicetree/bindings/dma/dma.txt
- dma-names: should include "tx".
- clocks: a list of phandle + clock-specifer pairs, one for each entry in clock-names.
- clock-names: should contain following:
   - "clk" : clock for Audio PWM controller
   - "hclk": clock for AHB BUS
- pinctrl-names: Must contain a "default" entry.
- pinctrl-N: One property must exist for each entry in
	     pinctrl-names. See ../pinctrl/pinctrl-bindings.txt
	     for details of the property values.

Optional properties:

- rockchip,sample-width-bits: Output sampling data width,the value ranges from 8 to 11 bits.
- rockchip,interpolat-points-cfg: Interpolation rate,the value must be 1/3/7/15 points,
  if this is set,the linear interpolation mode will be turned on.
- spk-ctl-gpios: The gpio of speak controller.

Example for Audio PWM controller:

audpwm: audpwm@ff840000 {
	compatible = "rockchip,audio-pwm-v1";
	reg = <0xff840000 0x1000>;
	clocks = <&cru SCLK_AUDPWM>, <&cru HCLK_AUDPWM>;
	clock-names = "clk", "hclk";
	dmas = <&dmac 26>;
	dma-names = "tx";
	pinctrl-names = "default";
	pinctrl-0 = <&audpwmm0_pins>;
	rockchip,sample-width-bits = <11>;
	rockchip,interpolat-points = <1>;
	spk-ctl-gpios = <&gpio0 RK_PC0 GPIO_ACTIVE_HIGH>;
	status = "disabled";
};