Binding for PWM driver for STMicroelectronics SoCs.

Required parameters:
- compatible : st,pwm
- #pwm-cells : number of cells used to specify a PWM.First cell specifies the per-chip
		index of the PWM to use and the second cell is the period in nanoseconds.
		Fixed to 2 for STiH41x.
- reg : physical base address and length of the controller's registers.
- pinctrl-names: Set to "default".
- pinctrl-0: List of phandles pointing to pin configuration nodes for PWM module.
	      For (4) & (5), please refer the following binding doc:
	      Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
- clock-names: Set to "pwm".
- clocks: phandle of the clock used by the PWM module.
	   For (6) & (7), please refer the following binding doc:
	   Documentation/devicetree/bindings/clock/clock-bindings.txt
Optional properties:
- st,pwm-num-chan: number of available channels. If not passed the driver will
  consider single channel by default.

Example:
pwm1: pwm@fe510000 {
	compatible = "st,pwm";
	#pwm-cells = <2>;
	reg = <0xfe510000 0x68>;
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_pwm1_chan0_default
		     &pinctrl_pwm1_chan1_default
		     &pinctrl_pwm1_chan2_default
		     &pinctrl_pwm1_chan3_default>;
	clock-names = "pwm";
	clocks = <&CLK_SYSIN>;
	st,pwm-num-chan = <4>;
};
