GPIO USB VBUS Detection

Discrete USB VBUS detection circuitry can be connected to the AP or PMICs.
Such circuits can be used to detect the when a USB cable is connected to
an upstream port such as a standard host or a wall charger by detecting
the presence of VBUS voltage. The GPIO can be configured to trigger an
interrupt, and allow the software driver to in turn notify the USB
subsytem using the power_supply framework.

Required Properties:
 - compatible: must be "qcom,gpio-usbdetect"
 - interrupts: an interrupt triggered by the output of the detection circuit
 - interrupt-names: must be "vbus_det_irq"

Optional Properties:
 - vin-supply: phandle to a regulator that powers this circuit, if needed

Example:

	usb_detect {
		compatible = "qcom,gpio-usbdetect";
                interrupt-parent = <&spmi_bus>;
                interrupts = <0x0 0xCA 0x0>;  /* PMA8084 GPIO 11 */
                interrupt-names = "vbus_det_irq";
                vin-supply = <&vbus_det_reg>;
	};