Documentation: Add examples to samsung-pinctrl device tree bindings documentation

  - gpio-controller: identifies the node as a gpio controller and pin bank.

  - #gpio-cells: number of cells in GPIO specifier. Since the generic GPIO

    binding is used, the amount of cells must be specified as 2. See generic

    GPIO binding documentation for description of particular cells.

    binding is used, the amount of cells must be specified as 2. See the below

    mentioned gpio binding representation for description of particular cells.

	Eg: <&gpx2 6 0>

	<[phandle of the gpio controller node]

	[pin number within the gpio controller]

	[flags]>

	Values for gpio specifier:

	- Pin number: is a value between 0 to 7.

	- Flags: 0 - Active High

		 1 - Active Low

- Pin mux/config groups as child nodes: The pin mux (selecting pin function

  mode) and pin config (pull up/down, driver strength) settings are represented

		pinctrl = devm_pinctrl_get_select_default(&pdev->dev);

	}

Example 5: A display port client node that supports 'default' pinctrl state

	   and gpio binding.

	display-port-controller {

		/* ... */

		samsung,hpd-gpio = <&gpx2 6 0>;

		pinctrl-names = "default";

		pinctrl-0 = <&dp_hpd>;

	};

Example 6: Request the gpio for display port controller

	static int exynos_dp_probe(struct platform_device *pdev)

	{

		int hpd_gpio, ret;

		struct device *dev = &pdev->dev;

		struct device_node *dp_node = dev->of_node;

		/* ... */

		hpd_gpio = of_get_named_gpio(dp_node, "samsung,hpd-gpio", 0);

		/* ... */

		ret = devm_gpio_request_one(&pdev->dev, hpd_gpio, GPIOF_IN,

					    "hpd_gpio");

		/* ... */

	}