tegra124 thermal throttle devicetree bindings

This device is used for thermal throttle, and has number of properties.

Required properties:
 - compatible:		we now support "nvidia,tegra124-tj-throttle".
 - clocks:		core shared clocks, we now support:
			cap.throttle.c3bus, cap.throttle.sclk, cap.throttl.emc
 - cpu-balanced-states	phandle of the cpu balanced throttle state.
Optional properties:
 - gpu-balanced-states	phandle of the gpu balanced throttle state.

====throttle state====
Required properties:
 - cpu-freq:		the limit of cpu freq in this throttle state.
Optional properties:
 - gpu-freq:		the limit of gpu freq in this throttle state.
			if omitted, it mean no limits for it.
 - c3bus-freq:		the limit of c3bus freq in this throttle state.
			if omitted, it mean no limits for it.
 - sclk-freq:		the limit of sclk freq in this throttle state.
			if omitted, it mean no limits for it.
 - emc-freq:		the limit of emc freq in this throttle state.
			if omitted, it mean no limits for it.

Example:
tj-temperature-throttling {
	compatible = "nvidia,tegra124-tj-throttle";
	clocks = <&tegra_car 418>, <&tegra_car 429>, <&tegra_car 459>;
	clock-names = "cap.throttle.c3bus", "cap.throttle.sclk", "cap.throttle.emc";
	cpu-balanced-states = <&{/cpu-throttling-state}>;
	gpu-balanced-states = <&{/gpu-throttling-state}>;
};

cpu-throttling-state {
	throt-state@0 {
		cpu-freq = <739500>;
		gpu-freq = <550000>;
	};
	throt-state@1 {
		cpu-freq = <714000>;
		c2bus-freq = <555000>;
	};
};

gpu-throttling-state {
	throt-state@0 {
		cpu-freq = <2295000>;
		gpu-freq = <782800>;
		c3bus-freq = <756000>;
		sclk-freq = <384000>;
		emc-freq = <924000>;
	};
};