ARM: dts: stm32: Enable EXTI on stm32mp13

As EXTI/GIC mapping has changed between STM32MP15 and STM32MP13, a new
compatible is needed to choose mp13 mapping table in stm32-exti driver.
Signed-off-by: NAlexandre Torgue <alexandre.torgue@foss.st.com>

arch/arm/boot/dts/stm32mp131.dtsi

@@ -159,6 +159,13 @@
 			dma-channels = <16>;
 		};
 
+		exti: interrupt-controller@5000d000 {
+			compatible = "st,stm32mp13-exti", "syscon";
+			interrupt-controller;
+			#interrupt-cells = <2>;
+			reg = <0x5000d000 0x400>;
+		};
+
 		syscfg: syscon@50020000 {
 			compatible = "st,stm32mp157-syscfg", "syscon";
 			reg = <0x50020000 0x400>;