regulator: tps65132: add device-tree binding

TPS65132 regulators

Required properties:

- compatible: "ti,tps65132"

- reg: I2C slave address

Optional Subnode:

Device supports two regulators OUTP and OUTN. A sub node within the

   device node describe the properties of these regulators. The sub-node

   names must be as follows:

	-For regulator outp, the sub node name should be "outp".

	-For regulator outn, the sub node name should be "outn".

-enable-gpios:(active high, output) Regulators are controlled by the input pins.

   If it is connected to GPIO through host system then provide the

   gpio number as per gpio.txt.

-active-discharge-gpios: (active high, output) Some configurations use delay mechanisms

  on the enable pin, to keep the regulator enabled for some time after

  the enable signal goes low. This GPIO is used to actively discharge

  the delay mechanism. Requires specification of ti,active-discharge-time-us

-ti,active-discharge-time-us: how long the active discharge gpio should be

  asserted for during active discharge, in microseconds.

Each regulator is defined using the standard binding for regulators.

Example:

	tps65132@3e {

		compatible = "ti,tps65132";

		reg = <0x3e>;

		outp {

			regulator-name = "outp";

			regulator-boot-on;

			regulator-always-on;

			enable-gpios = <&gpio 23 0>;

		};

		outn {

			regulator-name = "outn";

			regulator-boot-on;

			regulator-always-on;

			regulator-active-discharge = <0>;

			enable-gpios = <&gpio 40 0>;

		};

	};