Allwinner sun4i and sun7i SoC PWM controller

Required properties:
  - compatible: should be one of:
    - "allwinner,sun4i-a10-pwm"
    - "allwinner,sun5i-a10s-pwm"
    - "allwinner,sun5i-a13-pwm"
    - "allwinner,sun7i-a20-pwm"
  - reg: physical base address and length of the controller's registers
  - #pwm-cells: should be 3. See pwm.txt in this directory for a description of
    the cells format.
  - clocks: From common clock binding, handle to the parent clock.

Example:

	pwm: pwm@01c20e00 {
		compatible = "allwinner,sun7i-a20-pwm";
		reg = <0x01c20e00 0xc>;
		clocks = <&osc24M>;
		#pwm-cells = <3>;
		status = "disabled";
	};
