ARM: dts: imx6sll-evk: use WDOG_B pin reset

i.MX6SLL EVK board has WDOG_B pin connected to the PMIC;

Add the WDOG_B pinctrl entry and 'fsl,ext-reset-output'
property to wdog node to let watchdog trigger a system
POR reset via the PMIC.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6sll-evk.dts

@@ -314,6 +314,12 @@ &usdhc3 {
 	status = "okay";
 };
 
+&wdog1 {
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_wdog1>;
+	fsl,ext-reset-output;
+};
+
 &iomuxc {
 	pinctrl_reg_sd3_vmmc: sd3vmmcgrp {
 		fsl,pins = <
@@ -479,4 +485,10 @@ pinctrl_pwm1: pmw1grp {
 			MX6SLL_PAD_PWM1__PWM1_OUT   0x110b0
 		>;
 	};
+
+	pinctrl_wdog1: wdog1grp	{
+		fsl,pins = <
+			MX6SLL_PAD_WDOG_B__WDOG1_B   0x170b0
+		>;
+	};
 };