arm64: dts: apm: Update X-Gene standby GPIO controller DTS entries

Update APM X-Gene standby GPIO controller DTS entries to enable it
as interrupt controller.

[dhdang: update patch subject]
Signed-off-by: NY Vo <yvo@apm.com>
Signed-off-by: NQuan Nguyen <qnguyen@apm.com>
Reviewed-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NDuc Dang <dhdang@apm.com>

arch/arm64/boot/dts/apm/apm-storm.dtsi

@@ -883,6 +883,9 @@
 					<0x0 0x2b 0x1>,
 					<0x0 0x2c 0x1>,
 					<0x0 0x2d 0x1>;
+			interrupt-parent = <&gic>;
+			#interrupt-cells = <2>;
+			interrupt-controller;
 		};
 
 		rtc: rtc@10510000 {