ARM: at91: dts: set #dma-cells to the correct value

Moving to generic DMA DT binding involves to set #dma-cells to 2.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
diff --git a/arch/arm/boot/dts/at91sam9n12.dtsi b/arch/arm/boot/dts/at91sam9n12.dtsi
index 7750f98..acc4526 100644
--- a/arch/arm/boot/dts/at91sam9n12.dtsi
+++ b/arch/arm/boot/dts/at91sam9n12.dtsi
@@ -110,6 +110,7 @@
 				compatible = "atmel,at91sam9g45-dma";
 				reg = <0xffffec00 0x200>;
 				interrupts = <20 4 0>;
+				#dma-cells = <2>;
 			};
 
 			pinctrl@fffff400 {