thunderbolt: Use kobj_to_dev() instead of container_of()

Doesn't really matter for an individual driver, but it may
get coppied to lots more. I consider it's a little tidy up.
Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/domain.c

@@ -275,7 +275,7 @@ static struct attribute *domain_attrs[] = {
 static umode_t domain_attr_is_visible(struct kobject *kobj,
 				      struct attribute *attr, int n)
 {
-	struct device *dev = container_of(kobj, struct device, kobj);
+	struct device *dev = kobj_to_dev(kobj);
 	struct tb *tb = container_of(dev, struct tb, dev);
 
 	if (attr == &dev_attr_boot_acl.attr) {

drivers/thunderbolt/switch.c

@@ -1648,7 +1648,7 @@ static struct attribute *switch_attrs[] = {
 static umode_t switch_attr_is_visible(struct kobject *kobj,
 				      struct attribute *attr, int n)
 {
-	struct device *dev = container_of(kobj, struct device, kobj);
+	struct device *dev = kobj_to_dev(kobj);
 	struct tb_switch *sw = tb_to_switch(dev);
 
 	if (attr == &dev_attr_device.attr) {