Binding for the GPIO extension bus found on some LaCie/Seagate boards
(Example: 2Big/5Big Network v2, 2Big NAS).

Required properties:
- compatible: "lacie,netxbig-gpio-ext".
- addr-gpios: GPIOs representing the address register (LSB -> MSB).
- data-gpios: GPIOs representing the data register (LSB -> MSB).
- enable-gpio: latches the new configuration (address, data) on raising edge.

Example:

netxbig_gpio_ext: netxbig-gpio-ext {
	compatible = "lacie,netxbig-gpio-ext";

	addr-gpios = <&gpio1 15 GPIO_ACTIVE_HIGH
		      &gpio1 16 GPIO_ACTIVE_HIGH
		      &gpio1 17 GPIO_ACTIVE_HIGH>;
	data-gpios = <&gpio1 12 GPIO_ACTIVE_HIGH
		      &gpio1 13 GPIO_ACTIVE_HIGH
		      &gpio1 14 GPIO_ACTIVE_HIGH>;
	enable-gpio = <&gpio0 29 GPIO_ACTIVE_HIGH>;
};