Semtech sx150x GPIO controller bindings

Required properties:
- compatible:
  - "sx1508q" for sx1508 GPIO controller
  - "sx1509q" for sx1509 GPIO controller
- #gpio-cells : Should be two.
  - first cell is the pin number
  - second cell is used to specify optional parameters (unused)
- gpio-controller : Marks the device node as a GPIO controller.
- reg: 7-bit I2C address.
- sx150x,reset_onprobe: If set to true, the driver will trigger
  a full reset of the chip at the beginning of the probe in order
  to place it in a known state.
- sx150x,oscio_is_gpo: If set to true, the driver will configure
  OSCIO as a GPO instead of as an oscillator, increasing the size
  of the GP(I)O pool created by this expander by one. The
  output-only GPO pin will be added at the end of the block.
- sx150x,pullup_ena: A bit-mask which enables or disables the pull-up
  resistor for each IO line in the expander. Setting the bit at
  position n will enable the pull-up for the IO at the corresponding
  offset. For chips with fewer than 16 IO pins, high-end bits are ignored.
- sx150x,pulldn_ena: A bit-mask which enables-or disables the pull-down
  resistor for each IO line in the expander. Setting the bit at position
  n will enable the pull-down for the IO at the corresponding offset.
  For chips with fewer than 16 IO pins, high-end bits are ignored.
- sx150x,float_ena: A bit-mask which enables-or disables open-drain
  operation for each IO line in the expander. Setting the bit at
  position n enables open-drain operation for the IO at the corresponding
  offset. Clearing the bit enables regular push-pull operation for that IO.
  For chips with fewer than 16 IO pins, high-end bits are ignored.
- sx150x,polarity: A bit-mask which enables polarity inversion for each IO line
  in the expander. Setting the bit at position n inverts the polarity of
  that IO line, while clearing it results in normal polarity. For chips with
  fewer than 16 IO pins, high-end bits are ignored.
- sx150x,reset_gpio: System GPIO number connected to NRESET of SX150x devices.
  If "sx150x,reset_onprobe" is true, then the reset_gpio is pulled from low
  to high to reset the SX150x device. (optional)
 - <supply-name>-supply: phandle to the regulator device
   Required "supply-name" examples are:
	"vdd" : 1.8v supply for sx150x (io-expander).

Example:

i2c@f9925000 {
   ioexp_gpios: io_exp@3e {
      #gpio-cells = <2>;
      gpio-controller;
      compatible = "sx1509q";
      reg = <0x3e>;
      sx150x,pullup_ena = <0x00>;
      sx150x,pulldn_ena = <0x00>;
      sx150x,float_ena  = <0x00>;
      sx150x,polarity = <0x00>;
      sx150x,reset_onprobe;
      sx150x,reset_gpio = <&msmgpio 138 0x00>;
      label = "ioexp-gpio";
      vdd-supply = <&pm8917_l6>;
   };
};

Usage:
gpio_test {
   compatible = "testcode";
   test_gpio = <&ioexp_gpios 5 0x00>;
};