watchdog: mpc8xxx_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
  This also drops the inaccurate message on remove; the driver won't be
  removed if the hardware watchdog is running, no matter if the watchdog
  device is open or not.
- 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>
Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/mpc8xxx_wdt.c

@@ -204,9 +204,10 @@ static int mpc8xxx_wdt_probe(struct platform_device *ofdev)
 	if (ddata->wdd.timeout < ddata->wdd.min_timeout)
 		ddata->wdd.timeout = ddata->wdd.min_timeout;
 
-	ret = watchdog_register_device(&ddata->wdd);
+	ret = devm_watchdog_register_device(dev, &ddata->wdd);
 	if (ret) {
-		dev_err(dev, "cannot register watchdog device (err=%d)\n", ret);
+		dev_err(dev, "cannot register watchdog device (err=%d)\n",
+			ret);
 		return ret;
 	}
 
@@ -218,17 +219,6 @@ static int mpc8xxx_wdt_probe(struct platform_device *ofdev)
 	return 0;
 }
 
-static int mpc8xxx_wdt_remove(struct platform_device *ofdev)
-{
-	struct mpc8xxx_wdt_ddata *ddata = platform_get_drvdata(ofdev);
-
-	dev_crit(&ofdev->dev, "Watchdog removed, expect the %s soon!\n",
-		 reset ? "reset" : "machine check exception");
-	watchdog_unregister_device(&ddata->wdd);
-
-	return 0;
-}
-
 static const struct of_device_id mpc8xxx_wdt_match[] = {
 	{
 		.compatible = "mpc83xx_wdt",
@@ -259,7 +249,6 @@ MODULE_DEVICE_TABLE(of, mpc8xxx_wdt_match);
 
 static struct platform_driver mpc8xxx_wdt_driver = {
 	.probe		= mpc8xxx_wdt_probe,
-	.remove		= mpc8xxx_wdt_remove,
 	.driver = {
 		.name = "mpc8xxx_wdt",
 		.of_match_table = mpc8xxx_wdt_match,