dt-bindings: arm: atmel: describe SECUMOD usage as a GPIO controller

The Security Module macrocell provides all necessary secure functions to avoid

voltage, temperature, frequency and mechanical attacks on the chip. It also

embeds secure memories that can be scrambled

embeds secure memories that can be scrambled.

The Security Module also offers the PIOBU pins which can be used as GPIO pins.

Note that they maintain their voltage during Backup/Self-refresh.

required properties:

- compatible: Should be "atmel,<chip>-secumod", "syscon".

  <chip> can be "sama5d2".

- reg: Should contain registers location and length

- gpio-controller:	Marks the port as GPIO controller.

- #gpio-cells:		There are 2. The pin number is the

			first, the second represents additional

			parameters such as GPIO_ACTIVE_HIGH/LOW.

	secumod@fc040000 {

		compatible = "atmel,sama5d2-secumod", "syscon";

		reg = <0xfc040000 0x100>;

		gpio-controller;

		#gpio-cells = <2>;

	};