i.mx6 Poweroff Driver

SNVS_LPCR in SNVS module can power off the whole system by pull
PMIC_ON_REQ low if PMIC_ON_REQ is connected with external PMIC.
If you don't want to use PMIC_ON_REQ as power on/off control,
please set status='disabled' to disable this driver.

Required Properties:
-compatible: "fsl,sec-v4.0-poweroff"
-reg: Specifies the physical address of the SNVS_LPCR register

Example:
	snvs@20cc000 {
		compatible = "fsl,sec-v4.0-mon", "simple-bus";
		#address-cells = <1>;
		#size-cells = <1>;
		ranges = <0 0x020cc000 0x4000>;
		.....
		snvs_poweroff: snvs-poweroff@38 {
			compatible = "fsl,sec-v4.0-poweroff";
			reg = <0x38 0x4>;
		};
	}
