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>