Tegra SoC PWFM controller

Required properties:
- compatible: Must be:
  - "nvidia,tegra20-pwm": for Tegra20
  - "nvidia,tegra30-pwm", "nvidia,tegra20-pwm": for Tegra30
  - "nvidia,tegra114-pwm", "nvidia,tegra20-pwm": for Tegra114
  - "nvidia,tegra124-pwm", "nvidia,tegra20-pwm": for Tegra124
  - "nvidia,tegra132-pwm", "nvidia,tegra20-pwm": for Tegra132
  - "nvidia,tegra210-pwm", "nvidia,tegra20-pwm": for Tegra210
  - "nvidia,tegra186-pwm": for Tegra186
- reg: physical base address and length of the controller's registers
- #pwm-cells: should be 2. See pwm.txt in this directory for a description of
  the cells format.
- clocks: Must contain one entry, for the module clock.
  See ../clocks/clock-bindings.txt for details.
- resets: Must contain an entry for each entry in reset-names.
  See ../reset/reset.txt for details.
- reset-names: Must include the following entries:
  - pwm

Example:

	pwm: pwm@7000a000 {
		compatible = "nvidia,tegra20-pwm";
		reg = <0x7000a000 0x100>;
		#pwm-cells = <2>;
		clocks = <&tegra_car 17>;
		resets = <&tegra_car 17>;
		reset-names = "pwm";
	};
