power: supply: core: simplify power_supply_class_init

Technically the sysfs attributes should be initialized
before the class is registered, since that will use them.
As a nice side effect this nicely simplifies the code,
since it allows dropping the helper variable.
Reviewed-by: Ricardo B. Marliere <ricardo@marliere.net>
Link: https://lore.kernel.org/r/20240301-psy-class-cleanup-v1-2-aebe8c4b6b08@collabora.comSigned-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/power_supply_core.c

@@ -1622,15 +1622,8 @@ EXPORT_SYMBOL_GPL(power_supply_get_drvdata);
 
 static int __init power_supply_class_init(void)
 {
-	int err;
-
-	err = class_register(&power_supply_class);
-	if (err)
-		return err;
-
 	power_supply_init_attrs();
-
-	return 0;
+	return class_register(&power_supply_class);
 }
 
 static void __exit power_supply_class_exit(void)