thermal: doc: Add details of thermal_zone_of_sensor_{register,unregister}

    It deletes the corresponding entry form /sys/class/thermal folder and

    unbind all the thermal cooling devices it uses.

1.1.3 struct thermal_zone_device *thermal_zone_of_sensor_register(

		struct device *dev, int sensor_id, void *data,

		const struct thermal_zone_of_device_ops *ops)

	This interface adds a new sensor to a DT thermal zone.

	This function will search the list of thermal zones described in

	device tree and look for the zone that refer to the sensor device

	pointed by dev->of_node as temperature providers. For the zone

	pointing to the sensor node, the sensor will be added to the DT

	thermal zone device.

	The parameters for this interface are:

	dev:		Device node of sensor containing valid node pointer in

			dev->of_node.

	sensor_id:	a sensor identifier, in case the sensor IP has more

			than one sensors

	data:		a private pointer (owned by the caller) that will be

			passed back, when a temperature reading is needed.

	ops:		struct thermal_zone_of_device_ops *.

			get_temp:	a pointer to a function that reads the

					sensor temperature. This is mandatory

					callback provided by sensor driver.

			get_trend: 	a pointer to a function that reads the

					sensor temperature trend.

			set_emul_temp:	a pointer to a function that sets

					sensor emulated temperature.

	The thermal zone temperature is provided by the get_temp() function

	pointer of thermal_zone_of_device_ops. When called, it will

	have the private pointer @data back.

	It returns error pointer if fails otherwise valid thermal zone device

	handle. Caller should check the return handle with IS_ERR() for finding

	whether success or not.

1.1.4 void thermal_zone_of_sensor_unregister(struct device *dev,

		struct thermal_zone_device *tzd)

	This interface unregisters a sensor from a DT thermal zone which was

	successfully added by interface thermal_zone_of_sensor_register().

	This function removes the sensor callbacks and private data from the

	thermal zone device registered with thermal_zone_of_sensor_register()

	interface. It will also silent the zone by remove the .get_temp() and

	get_trend() thermal zone device callbacks.

1.2 thermal cooling device interface

1.2.1 struct thermal_cooling_device *thermal_cooling_device_register(char *name,

		void *devdata, struct thermal_cooling_device_ops *)