Hisilicon PWM controller

Required properties:
-compatible: should contain one SoC specific compatible string
 The SoC specific strings supported including:
	"hisilicon,hi3516cv300-pwm"
	"hisilicon,hi3519v100-pwm"
	"hisilicon,hi3559v100-shub-pwm"
	"hisilicon,hi3559v100-pwm
- reg: physical base address and length of the controller's registers.
- clocks: phandle and clock specifier of the PWM reference clock.
- resets: phandle and reset specifier for the PWM controller reset.
- #pwm-cells: Should be 3. See pwm.yaml in this directory for a description of
  the cells format.

Example:
	pwm: pwm@12130000 {
		compatible = "hisilicon,hi3516cv300-pwm";
		reg = <0x12130000 0x10000>;
		clocks = <&crg_ctrl HI3516CV300_PWM_CLK>;
		resets = <&crg_ctrl 0x38 0>;
		#pwm-cells = <3>;
	};
