watchdog: max77620_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
- Introduce local variable 'struct device *dev' and use it instead of
  dereferencing it repeatedly
- Replace stop on remove with call to watchdog_stop_on_unregister()
- 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/max77620_wdt.c

@@ -112,17 +112,18 @@ static const struct watchdog_ops max77620_wdt_ops = {
 
 static int max77620_wdt_probe(struct platform_device *pdev)
 {
+	struct device *dev = &pdev->dev;
 	struct max77620_wdt *wdt;
 	struct watchdog_device *wdt_dev;
 	unsigned int regval;
 	int ret;
 
-	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
+	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
 	if (!wdt)
 		return -ENOMEM;
 
-	wdt->dev = &pdev->dev;
-	wdt->rmap = dev_get_regmap(pdev->dev.parent, NULL);
+	wdt->dev = dev;
+	wdt->rmap = dev_get_regmap(dev->parent, NULL);
 	if (!wdt->rmap) {
 		dev_err(wdt->dev, "Failed to get parent regmap\n");
 		return -ENODEV;
@@ -183,25 +184,16 @@ static int max77620_wdt_probe(struct platform_device *pdev)
 	watchdog_set_nowayout(wdt_dev, nowayout);
 	watchdog_set_drvdata(wdt_dev, wdt);
 
-	ret = watchdog_register_device(wdt_dev);
+	watchdog_stop_on_unregister(wdt_dev);
+	ret = devm_watchdog_register_device(dev, wdt_dev);
 	if (ret < 0) {
-		dev_err(&pdev->dev, "watchdog registration failed: %d\n", ret);
+		dev_err(dev, "watchdog registration failed: %d\n", ret);
 		return ret;
 	}
 
 	return 0;
 }
 
-static int max77620_wdt_remove(struct platform_device *pdev)
-{
-	struct max77620_wdt *wdt = platform_get_drvdata(pdev);
-
-	max77620_wdt_stop(&wdt->wdt_dev);
-	watchdog_unregister_device(&wdt->wdt_dev);
-
-	return 0;
-}
-
 static const struct platform_device_id max77620_wdt_devtype[] = {
 	{ .name = "max77620-watchdog", },
 	{ },
@@ -213,7 +205,6 @@ static struct platform_driver max77620_wdt_driver = {
 		.name	= "max77620-watchdog",
 	},
 	.probe	= max77620_wdt_probe,
-	.remove	= max77620_wdt_remove,
 	.id_table = max77620_wdt_devtype,
 };