iio: imu: adis16480: Add docs for ADIS16480 IMU

Analog Devices ADIS16480 and similar IMUs

Required properties for the ADIS16480:

- compatible: Must be one of

	* "adi,adis16375"

	* "adi,adis16480"

	* "adi,adis16485"

	* "adi,adis16488"

	* "adi,adis16495-1"

	* "adi,adis16495-2"

	* "adi,adis16495-3"

	* "adi,adis16497-1"

	* "adi,adis16497-2"

	* "adi,adis16497-3"

- reg: SPI chip select number for the device

- spi-max-frequency: Max SPI frequency to use

	see: Documentation/devicetree/bindings/spi/spi-bus.txt

- spi-cpha: See Documentation/devicetree/bindings/spi/spi-bus.txt

- spi-cpol: See Documentation/devicetree/bindings/spi/spi-bus.txt

- interrupts: interrupt mapping for IRQ, accepted values are:

	* IRQF_TRIGGER_RISING

	* IRQF_TRIGGER_FALLING

Optional properties:

- interrupt-names: Data ready line selection. Valid values are:

	* DIO1

	* DIO2

	* DIO3

	* DIO4

	If this field is left empty, DIO1 is assigned as default data ready

	signal.

- reset-gpios: must be the device tree identifier of the RESET pin. As the line

	is active low, it should be marked GPIO_ACTIVE_LOW.

Example:

	imu@0 {

		compatible = "adi,adis16495-1";

		reg = <0>;

		spi-max-frequency = <3200000>;

		spi-cpol;

		spi-cpha;

		interrupts = <25 IRQF_TRIGGER_FALLING>;

		interrupt-parent = <&gpio>;

		interrupt-names = "DIO2";

	};

ANALOG DEVICES INC IIO DRIVERS

M:	Lars-Peter Clausen <lars@metafoo.de>

M:	Michael Hennerich <Michael.Hennerich@analog.com>

M:	Stefan Popa <stefan.popa@analog.com>

W:	http://wiki.analog.com/

W:	http://ez.analog.com/community/linux-device-drivers

S:	Supported