watchdog: sbsa_gwdt: 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
- Replace shutdown function with call to watchdog_stop_on_reboot()
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/sbsa_gwdt.c

@@ -310,7 +310,8 @@ static int sbsa_gwdt_probe(struct platform_device *pdev)
 	 */
 	sbsa_gwdt_set_timeout(wdd, wdd->timeout);
 
-	ret = watchdog_register_device(wdd);
+	watchdog_stop_on_reboot(wdd);
+	ret = devm_watchdog_register_device(dev, wdd);
 	if (ret)
 		return ret;
 
@@ -321,22 +322,6 @@ static int sbsa_gwdt_probe(struct platform_device *pdev)
 	return 0;
 }
 
-static void sbsa_gwdt_shutdown(struct platform_device *pdev)
-{
-	struct sbsa_gwdt *gwdt = platform_get_drvdata(pdev);
-
-	sbsa_gwdt_stop(&gwdt->wdd);
-}
-
-static int sbsa_gwdt_remove(struct platform_device *pdev)
-{
-	struct sbsa_gwdt *gwdt = platform_get_drvdata(pdev);
-
-	watchdog_unregister_device(&gwdt->wdd);
-
-	return 0;
-}
-
 /* Disable watchdog if it is active during suspend */
 static int __maybe_unused sbsa_gwdt_suspend(struct device *dev)
 {
@@ -382,8 +367,6 @@ static struct platform_driver sbsa_gwdt_driver = {
 		.of_match_table = sbsa_gwdt_of_match,
 	},
 	.probe = sbsa_gwdt_probe,
-	.remove = sbsa_gwdt_remove,
-	.shutdown = sbsa_gwdt_shutdown,
 	.id_table = sbsa_gwdt_pdev_match,
 };