watchdog: stmp3xxx_rtc_wdt: Convert to use device managed functions

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

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

- Introduce local variable 'struct device *dev' and use it instead of
  dereferencing it repeatedly
- Use devm_watchdog_register_driver() to register watchdog device

Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/stmp3xxx_rtc_wdt.c

@@ -89,31 +89,31 @@ static struct notifier_block wdt_notifier = {
 
 static int stmp3xxx_wdt_probe(struct platform_device *pdev)
 {
+	struct device *dev = &pdev->dev;
 	int ret;
 
-	watchdog_set_drvdata(&stmp3xxx_wdd, &pdev->dev);
+	watchdog_set_drvdata(&stmp3xxx_wdd, dev);
 
 	stmp3xxx_wdd.timeout = clamp_t(unsigned, heartbeat, 1, STMP3XXX_MAX_TIMEOUT);
-	stmp3xxx_wdd.parent = &pdev->dev;
+	stmp3xxx_wdd.parent = dev;
 
-	ret = watchdog_register_device(&stmp3xxx_wdd);
+	ret = devm_watchdog_register_device(dev, &stmp3xxx_wdd);
 	if (ret < 0) {
-		dev_err(&pdev->dev, "cannot register watchdog device\n");
+		dev_err(dev, "cannot register watchdog device\n");
 		return ret;
 	}
 
 	if (register_reboot_notifier(&wdt_notifier))
-		dev_warn(&pdev->dev, "cannot register reboot notifier\n");
+		dev_warn(dev, "cannot register reboot notifier\n");
 
-	dev_info(&pdev->dev, "initialized watchdog with heartbeat %ds\n",
-			stmp3xxx_wdd.timeout);
+	dev_info(dev, "initialized watchdog with heartbeat %ds\n",
+		 stmp3xxx_wdd.timeout);
 	return 0;
 }
 
 static int stmp3xxx_wdt_remove(struct platform_device *pdev)
 {
 	unregister_reboot_notifier(&wdt_notifier);
-	watchdog_unregister_device(&stmp3xxx_wdd);
 	return 0;
 }