drm/virtio: advertise features to userspace

New api changes are now available to userspace. Also, the
comparison to true is redundant, so remove it.

Signed-off-by: Gurchetan Singh <gurchetansingh@chromium.org>
Acked-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20200924003214.662-19-gurchetansingh@chromium.org


Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>