ARM: at91: at91sam9n12: move external irq declatation to DT

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.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 3de8e6d..8d25f88 100644
--- a/arch/arm/boot/dts/at91sam9n12.dtsi
+++ b/arch/arm/boot/dts/at91sam9n12.dtsi
@@ -57,6 +57,7 @@
 				compatible = "atmel,at91rm9200-aic";
 				interrupt-controller;
 				reg = <0xfffff000 0x200>;
+				atmel,external-irqs = <31>;
 			};
 
 			ramc0: ramc@ffffe800 {