* LTR 558/659 ALS/proximity sensor

nvs_ drivers use the NVidia Sensor (NVS) framework.
See the nvs.txt documentation for NVS DT capabilities.
The nvs_ltr659 ALS/proximity sensor driver supports the LTR558 and LTR659
devices.
If the part is known and is populated, then it can be specified in the DT:
Example: ltr659@23.
By specifying a device this way, the driver will assume this specific device
is populated during system boot and will not verify its existence. If, however,
the device is unknown or may not be populated, then the label, ltrX5X,
(e.g. ltrX5X@23), must be used.  This tells the driver to find which device is
used.  If the device is not found, the driver will unload itself.  This also
requires that regulators be setup correctly for the probe function.

Required properties:
- compatible: Device or generic name.
	      Supported device names:
	      - liteon,ltrX5X
	      - liteon,ltr558als
	      - liteon,ltr659ps
  Note: If the part is known and is populated, then it can be specified:
	Example: compatible = "liteon,ltr659ps";
	When specifying a device this way, the driver will assume this specific
	device is populated during system boot and will not verify its
	existence.  If, however, the device is unknown or may not be populated,
	then the label, ltrX5X, (Example: compatible = "liteon,ltrX5X";),
	must be used.  This tells the driver to find which device is used.  If
	the device is not found, the driver will unload itself.  This requires
	regulators to be setup correctly for the probe function.
- reg: i2c address of the device. It is 0x23.

Optional properties:
- status: set to "ok" or "okay" for normal operation.  Set to anything else
	  to unload the driver without ever communicating with the device.
  Note: The "anything else" above is typically "disabled".
	Since the driver will unload without communicating with the device, the
	device will be left in its POR state.
- light_disable: Setting this property to <1> will disable the light sensor.
- proximity_disable: Setting this property to <1> will disable the proximity
                     sensor.
  Note: If the device supports both light and proximity, then to disable the
        entire device so that the driver unloads, all sensors must be disabled:
	light_disable = <1>;
	proximity_disable = <1>;
- vdd-supply: regulator supply for chip
- vled-supply: regulator supply for led anode.
  Note: These are required if the driver is to control the regulators.

Example:

	ltr659@23 {
		compatible = "liteon,ltr659";
		reg = <0x23>;
		vdd-supply = <&palmas_smps9>;
		vled-supply = <&palmas_smps8>;
	};