ARM: dts: imx6ul: add pm_power_off support

i.MX6UL can be powered off by programming SNVS.

When long press ON/OFF button(5 seconds),
PMIC_ON_REQ pin will be set to low and external
PMIC will be powered off.

And system can be powered on by long press ON/OFF
button again.
Signed-off-by: Anson Huang <b20788@freescale.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6ul-14x14-evk.dts

@@ -87,6 +87,10 @@ flash0: n25q256a@0 {
 	};
 };
 
+&snvs_poweroff {
+	status = "okay";
+};
+
 &uart1 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_uart1>;

arch/arm/boot/dts/imx6ul.dtsi

@@ -429,6 +429,14 @@ snvs_rtc: snvs-rtc-lp {
 						     <GIC_SPI 20 IRQ_TYPE_LEVEL_HIGH>;
 				};
 
+				snvs_poweroff: snvs-poweroff {
+					compatible = "syscon-poweroff";
+					regmap = <&snvs>;
+					offset = <0x38>;
+					mask = <0x60>;
+					status = "disabled";
+				};
+
 				snvs_pwrkey: snvs-powerkey {
 					compatible = "fsl,sec-v4.0-pwrkey";
 					regmap = <&snvs>;