ARM: dts: at91: sama5d2: mark secumod as a GPIO controller

The Security Module exposes the PIOBU pins which an be used
as regular GPIOs. The PIOBU pins are special because they do
not lose their voltage during suspend-to-mem.

This patch marks the secumod as a GPIO controller.
Signed-off-by: Andrei Stefanescu <andrei.stefanescu@microchip.com>
[razvan.stefanescu@microchip.com Updated title]
Signed-off-by: Razvan Stefanescu <razvan.stefanescu@microchip.com>
Link: https://lore.kernel.org/r/1573543139-8533-2-git-send-email-eugen.hristev@microchip.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

arch/arm/boot/dts/sama5d2.dtsi

@@ -885,9 +885,12 @@ pioA: pinctrl@fc038000 {
 				clocks = <&pmc PMC_TYPE_PERIPHERAL 18>;
 			};
 
-			secumod@fc040000 {
+			pioBU: secumod@fc040000 {
 				compatible = "atmel,sama5d2-secumod", "syscon";
 				reg = <0xfc040000 0x100>;
+
+				gpio-controller;
+				#gpio-cells = <2>;
 			};
 
 			tdes@fc044000 {