[RFC v2 05/11] block: add infra to handle dmabuf tokens

[Anuj gupta]

> +
> +       dma_fence_init(&fence->base, &blk_mq_dma_fence_ops, &fence->lock,
> +                       token->fence_ctx, atomic_inc_return(&token->fence_seq));
> +       spin_lock_init(&fence->lock);

nit lock should be initialized before handing its address to
dma_fence_init()