improve vivante_update_fence(..) situation

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
remove duplicated vivante_update_fence(..) call

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
there is no need for a fence callback

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>