Bindings for a fan connected to the PWM lines

Properties details:
- compatible		: "pwm-fan"
- pwms			: the PWM that is used to control the PWM fan

- shared_data
  - active_steps	: Entries for references in active_rpm[], active_pwm[], active_rru[], active_rrd[]
  - active_rru		: This value is kept on added to cur_pwm till it reaches at
			  next active step from the table. This is repeated until cur_pwm
			  value reaches target_pwm
  - active_rrd		: This value is kept on subtracted from cur_pwm till it reaches at
			  previous active step from the table. This is repeated until cur_pwm
			  value reaches target_pwm
  - state_cap_lookup 	: Index to refer in active_pwm[]
  - pwm_period		: To derive duty cycle
  - pwm_id		: Assigned PWM controller id to tegra fan
			  Same as mentioned id in pwms. In pwms, the id starts from 1
			  pwm_id in pfsd, the id starts from 0
  - step_time		: Time taken for each step during rru/rrd
  - state_cap		: Capping state value out of available active_steps
  - active_pwm_max	: Max pwm value (256)
  - pwm_gpio		: GPIO pin used for pwm

Example:

	pwm_fan_shared_data: pfsd {
		status = "okay";
		num_resources = <0>;
		active_steps = <10>;
		active_rpm = <0 1000 2000 3000 4000 5000 6000 7000 10000 11000>;
		active_rru = <40 2 1 1 1 1 1 1 1 1>;
		active_rrd = <40 2 1 1 1 1 1 1 1 1>;
		state_cap_lookup = <2 2 2 2 3 3 3 4 4 4>;
		pwm_period = <45334>;
		pwm_id = <3>;
		step_time = <100>; /* mesecs */
		state_cap = <7>;
		active_pwm_max = <256>;
		pwm_gpio = <&tegra_aon_gpio TEGRA_AON_GPIO(V, 6) GPIO_ACTIVE_LOW>; /* TEGRA_MAIN_GPIO_PV6 */
	};
	pwm-fan {
		status = "okay";
		compatible = "pwm-fan";
		#pwm-cells = <1>;
		pwms = <&tegra_pwm4 0 45334>;
		shared_data = <&pwm_fan_shared_data>;
		active_pwm = <0 80 120 160 255 255 255 255 255 255>;
	};
};