arm64: dts: ls208xa-rdb: add interrupt line for RTC node

Add interrupt line for RTC node on ls208xa-rdb
Signed-off-by: Biwen Li <biwen.li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/fsl-ls208xa-rdb.dtsi

@@ -3,7 +3,7 @@
  * Device Tree file for Freescale LS2080A RDB Board.
  *
  * Copyright 2016 Freescale Semiconductor, Inc.
- * Copyright 2017 NXP
+ * Copyright 2017-2020 NXP
  *
  * Abhimanyu Saini <abhimanyu.saini@nxp.com>
  *
@@ -56,6 +56,8 @@ i2c@1 {
 			rtc@68 {
 				compatible = "dallas,ds3232";
 				reg = <0x68>;
+				/* IRQ_RTC_B -> IRQ06, active low */
+				interrupts-extended = <&extirq 6 IRQ_TYPE_LEVEL_LOW>;
 			};
 		};