arm64: dts: mba8xx: Add missing #interrupt-cells

The GPIO expander is a interrupt-controller, so add the missing
 #interrupt-cells property as well.

Fixes: 71363a48 ("arm64: dts: freescale: add initial device tree for TQMa8Xx")
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/mba8xx.dtsi

@@ -240,6 +240,7 @@ expander: gpio@70 {
 		interrupt-parent = <&lsio_gpio4>;
 		interrupts = <19 IRQ_TYPE_LEVEL_LOW>;
 		interrupt-controller;
+		#interrupt-cells = <2>;
 		vcc-supply = <&reg_1v8>;
 
 		gpio-line-names = "", "LED_A",