drivers/video/udlfb match class, subclass, and protocol

Match udlfb only against vendor-specific class (e.g. only DisplayLink
graphics, not composite standard audio class interfaces). This enables
compatibility with composite graphics+audio devices (e.g. HDMI).

Match udlfb only against compatible subclass 0 and protocol 0 chips.
DisplayLink's USB 3.0 generation chips increment these values
to signal that they have a incompatible protocol, preventing udlfb
from erroneously matching to hardware it does not support.

Tested to confirm proper behavior on both USB 2.0 and USB 3.0
generation devices.

Reported-by: Andrew Kephart <akephart@akephart.org>
Signed-off-by: Bernie Thompson <bernie@plugable.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>