watchdog: gpio_wdt: Convert to use device managed functions and other improvements

Use device managed functions to simplify error handling, reduce
source code size, improve readability, and reduce the likelyhood of bugs.
Other improvements as listed below.

The conversion was done automatically with coccinelle using the
following semantic patches. The semantic patches and the scripts
used to generate this commit log are available at
https://github.com/groeck/coccinelle-patches

- Drop assignments to otherwise unused variables
- Drop empty remove function
- Use local variable 'struct device *dev' consistently
- Use devm_watchdog_register_driver() to register watchdog device
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/gpio_wdt.c

@@ -154,25 +154,14 @@ static int gpio_wdt_probe(struct platform_device *pdev)
 	priv->wdd.parent	= dev;
 	priv->wdd.timeout	= SOFT_TIMEOUT_DEF;
 
-	watchdog_init_timeout(&priv->wdd, 0, &pdev->dev);
+	watchdog_init_timeout(&priv->wdd, 0, dev);
 
 	watchdog_stop_on_reboot(&priv->wdd);
 
 	if (priv->always_running)
 		gpio_wdt_start(&priv->wdd);
 
-	ret = watchdog_register_device(&priv->wdd);
-
-	return ret;
-}
-
-static int gpio_wdt_remove(struct platform_device *pdev)
-{
-	struct gpio_wdt_priv *priv = platform_get_drvdata(pdev);
-
-	watchdog_unregister_device(&priv->wdd);
-
-	return 0;
+	return devm_watchdog_register_device(dev, &priv->wdd);
 }
 
 static const struct of_device_id gpio_wdt_dt_ids[] = {
@@ -187,7 +176,6 @@ static struct platform_driver gpio_wdt_driver = {
 		.of_match_table	= gpio_wdt_dt_ids,
 	},
 	.probe	= gpio_wdt_probe,
-	.remove	= gpio_wdt_remove,
 };
 
 #ifdef CONFIG_GPIO_WATCHDOG_ARCH_INITCALL