powerpc/secvar: fix refcount leak in format_show()

Refcount leak will happen when format_show returns failure in multiple
cases. Unified management of of_node_put can fix this problem.
Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220302021959.10959-1-hbh25y@gmail.com

arch/powerpc/kernel/secvar-sysfs.c

@@ -26,15 +26,18 @@ static ssize_t format_show(struct kobject *kobj, struct kobj_attribute *attr,
 	const char *format;
 
 	node = of_find_compatible_node(NULL, NULL, "ibm,secvar-backend");
-	if (!of_device_is_available(node))
-		return -ENODEV;
+	if (!of_device_is_available(node)) {
+		rc = -ENODEV;
+		goto out;
+	}
 
 	rc = of_property_read_string(node, "format", &format);
 	if (rc)
-		return rc;
+		goto out;
 
 	rc = sprintf(buf, "%s\n", format);
 
+out:
 	of_node_put(node);
 
 	return rc;