drm/nouveau/kms: handle mDP connectors

commit d1f5a3fc

 upstream.

In some cases we have the handle those explicitly as the fallback
connector type detection fails and marks those as eDP connectors.

Attempting to use such a connector with mutter leads to a crash of mutter
as it ends up with two eDP displays.

Information is taken from the official DCB documentation.

Cc: stable@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: Ben Skeggs <bskeggs@redhat.com>
Reported-by: Mark Pearson <markpearson@lenovo.com>
Tested-by: Mark Pearson <markpearson@lenovo.com>
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>