HID: elo: update the reference count of the usb device structure

Use usb_get_dev() to increment the reference count of the usb device
structure in order to avoid releasing the structure while it is still in
use. And use usb_put_dev() to decrement the reference count and thus,
when it will be equal to 0 the structure will be released.
Signed-off-by: Salah Triki <salah.triki@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-elo.c

@@ -228,13 +228,15 @@ static int elo_probe(struct hid_device *hdev, const struct hid_device_id *id)
 {
 	struct elo_priv *priv;
 	int ret;
+	struct usb_device *udev;
 
 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;
 
 	INIT_DELAYED_WORK(&priv->work, elo_work);
-	priv->usbdev = interface_to_usbdev(to_usb_interface(hdev->dev.parent));
+	udev = interface_to_usbdev(to_usb_interface(hdev->dev.parent));
+	priv->usbdev = usb_get_dev(udev);
 
 	hid_set_drvdata(hdev, priv);
 
@@ -265,6 +267,8 @@ static void elo_remove(struct hid_device *hdev)
 {
 	struct elo_priv *priv = hid_get_drvdata(hdev);
 
+	usb_put_dev(priv->usbdev);
+
 	hid_hw_stop(hdev);
 	cancel_delayed_work_sync(&priv->work);
 	kfree(priv);