ARM: dts: imx6qdl-sabresd: Use WDOG_B pin reset

imx6qdl-sabresd has WDOG2_B pin connected to the PMIC.

Pass the 'fsl,ext-reset-output' property so that the watchdog
can trigger a system POR reset via the PMIC.
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6qdl-sabresd.dtsi

@@ -501,6 +501,12 @@ MX6QDL_PAD_SD4_DAT6__SD4_DATA6		0x17059
 				MX6QDL_PAD_SD4_DAT7__SD4_DATA7		0x17059
 			>;
 		};
+
+		pinctrl_wdog: wdoggrp {
+			fsl,pins = <
+				MX6QDL_PAD_GPIO_1__WDOG2_B		0x1b0b0
+			>;
+		};
 	};
 
 	gpio_leds {
@@ -596,3 +602,14 @@ &usdhc4 {
 	no-1-8-v;
 	status = "okay";
 };
+
+&wdog1 {
+	status = "disabled";
+};
+
+&wdog2 {
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_wdog>;
+	fsl,ext-reset-output;
+	status = "okay";
+};