drm/usb: bind driver to correct device

While looking at plymouth on udl I noticed that plymouth was trying
to use its fb plugin not its drm one, it was trying to drmOpen a driver called
usb not udl, noticed that we actually had out driver pointing at the wrong
device.

Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/drm_usb.c b/drivers/gpu/drm/drm_usb.c
index 3cec306..34a156f 100644
--- a/drivers/gpu/drm/drm_usb.c
+++ b/drivers/gpu/drm/drm_usb.c
@@ -18,7 +18,7 @@
 
 	usbdev = interface_to_usbdev(interface);
 	dev->usbdev = usbdev;
-	dev->dev = &usbdev->dev;
+	dev->dev = &interface->dev;
 
 	mutex_lock(&drm_global_mutex);