HID: use kobj_to_dev()

Use kobj_to_dev() instead of open-coding it.

Signed-off-by: Geliang Tang <geliangtang@163.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/hid/wacom_sys.c b/drivers/hid/wacom_sys.c
index 4b7feb3..a90de9b 100644
--- a/drivers/hid/wacom_sys.c
+++ b/drivers/hid/wacom_sys.c
@@ -1130,7 +1130,7 @@
 				      struct kobj_attribute *kattr,
 				      char *buf, int index)
 {
-	struct device *dev = container_of(kobj->parent, struct device, kobj);
+	struct device *dev = kobj_to_dev(kobj->parent);
 	struct hid_device *hdev = to_hid_device(dev);
 	struct wacom *wacom = hid_get_drvdata(hdev);
 	u8 mode;
@@ -1241,7 +1241,7 @@
 					 const char *buf, size_t count)
 {
 	unsigned char selector = 0;
-	struct device *dev = container_of(kobj->parent, struct device, kobj);
+	struct device *dev = kobj_to_dev(kobj->parent);
 	struct hid_device *hdev = to_hid_device(dev);
 	struct wacom *wacom = hid_get_drvdata(hdev);
 	int err;