drm/virtio: implement context init: stop using drv->context when creating fence

drm/virtio: implement context init: stop using drv->context when creating fence

The plumbing is all here to do this.  Since we always use the
default fence context when allocating a fence, this makes no
functional difference.

We can't process just the largest fence id anymore, since it's
it's associated with different timelines.  It's fine for fence_id
260 to signal before 259.  As such, process each fence_id
individually.

Signed-off-by: Gurchetan Singh <gurchetansingh@chromium.org>
Acked-by: Lingfeng Yang <lfy@google.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20210921232024.817-9-gurchetansingh@chromium.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>