Binding for NVS LED Test driver

Required Properties:
 - compatible: "nvidia,nvs-led-test"
 - out-gpios: GPIO which is used to light up an attached LED. This will be
              driven high when the driver fires off a sensor event. The
              GPIO will remain high for a time interval = the value written
              to the on_ms sysfs entry.

Optional Properties:
 - enable-gpio: GPIO which is required to be enabled in order for the
                attached LED to toggle as expected.

Example:

nvs-led-test {
	compatible = "nvidia,nvs-led-test";
	out-gpios = <&tegra_main_gpio TEGRA_MAIN_GPIO(D, 3) 0>;
	status = "okay";
};
