drm/virtio: Add fences for Guest blobs

Add prepare and cleanup routines for primary planes as well
where a fence is added only if the BO/FB associated with the
plane is a guest blob.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20210610232456.671905-2-vivek.kasireddy@intel.com


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