GPIO via CREG (control registers) driver

31                 9        7        5           0   < bit number
|                  |        |        |           |
[     not used     | gpio-1 | gpio-0 | <-shift-> ]   < 32 bit register
                       ^        ^
                       |        |
                write 0x2 == set output to "1" (activate)
                write 0x3 == set output to "0" (deactivate)

Required properties:
- compatible : "snps,creg-gpio"
- reg : Exactly one register range with length 0x4.
- #gpio-cells : Should be one - the pin number.
- gpio-controller : Marks the device node as a GPIO controller.
- gpio-count: Number of GPIO pins.
- gpio-bit-per-line: Number of bits per gpio line (see picture).
- gpio-first-shift: Shift (in bits) of the first GPIO field in register
  (see picture).
- gpio-activate-val: Value should be set in corresponding field to set
  output to "1" (see picture). Applied to all GPIO ports.
- gpio-deactivate-val: Value should be set in corresponding field to set
  output to "0" (see picture). Applied to all GPIO ports.

Optional properties:
- gpio-bank-name: name of bank (as default driver name is used is used)
- gpio-default-val: array of default output values (must me 0 or 1)

Example (see picture):

gpio: gpio@f00014b0 {
	compatible = "snps,creg-gpio";
	reg = <0xf00014b0 0x4>;
	gpio-controller;
	#gpio-cells = <1>;
	gpio-bank-name = "hsdk-spi-cs";
	gpio-count = <2>;
	gpio-first-shift = <5>;
	gpio-bit-per-line = <2>;
	gpio-activate-val = <2>;
	gpio-deactivate-val = <3>;
	gpio-default-val = <1 1>;
};