gpio: palmas: add dt support

Add of_device_id table for Palma GPIO to be enable the
driver from DT file.

The driver can be registered from DT file as:
palmas: tps65913@58 {
:::::::::::
palmas_gpio: palmas_gpio {
compatible = "ti,palmas-gpio";
gpio-controller;
#gpio-cells = <2>;
};
};

Signed-off-by: Laxman Dewangan <[e-mail]>
Acked-by: Stephen Warren <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

Documentation/devicetree/bindings/gpio/gpio-palmas.txt

···
+Palmas GPIO controller bindings
+
+Required properties:
+- compatible:
+  - "ti,palams-gpio" for palma series of the GPIO controller
+  - "ti,tps80036-gpio" for Palma series device TPS80036.
+  - "ti,tps65913-gpio" for palma series device TPS65913.
+  - "ti,tps65914-gpio" for palma series device TPS65914.
+- #gpio-cells : Should be two.
+  - first cell is the gpio pin number
+  - second cell is used to specify the gpio polarity:
+      0 = active high
+      1 = active low
+- gpio-controller : Marks the device node as a GPIO controller.
+
+Note: This gpio node will be sub node of palmas node.
+
+Example:
+	palmas: tps65913@58 {
+		:::::::::::
+		palmas_gpio: palmas_gpio {
+			compatible = "ti,palmas-gpio";
+			gpio-controller;
+			#gpio-cells = <2>;
+		};
+		:::::::::::
+	};

drivers/gpio/gpio-palmas.c

···
 	palmas_gpio->gpio_chip.get	= palmas_gpio_get;
 	palmas_gpio->gpio_chip.dev = &pdev->dev;
 #ifdef CONFIG_OF_GPIO
-	palmas_gpio->gpio_chip.of_node = palmas->dev->of_node;
+	palmas_gpio->gpio_chip.of_node = pdev->dev.of_node;
 #endif
 	palmas_pdata = dev_get_platdata(palmas->dev);
 	if (palmas_pdata && palmas_pdata->gpio_base)
···
 	return gpiochip_remove(&palmas_gpio->gpio_chip);
 }
 
+static struct of_device_id of_palmas_gpio_match[] = {
+	{ .compatible = "ti,palmas-gpio"},
+	{ .compatible = "ti,tps65913-gpio"},
+	{ .compatible = "ti,tps65914-gpio"},
+	{ .compatible = "ti,tps80036-gpio"},
+	{ },
+};
+MODULE_DEVICE_TABLE(of, of_palmas_gpio_match);
+
 static struct platform_driver palmas_gpio_driver = {
 	.driver.name	= "palmas-gpio",
 	.driver.owner	= THIS_MODULE,
+	.driver.of_match_table = of_palmas_gpio_match,
 	.probe		= palmas_gpio_probe,
 	.remove		= palmas_gpio_remove,
 };