In preparation for switching single segment iterators to using ITER_UBUF,
swap the check for whether we are user backed or not.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
        if (runtime->state == SNDRV_PCM_STATE_OPEN ||
            runtime->state == SNDRV_PCM_STATE_DISCONNECTED)
                return -EBADFD;
-       if (!iter_is_iovec(to))
+       if (!to->user_backed)
                return -EINVAL;
        if (to->nr_segs > 1024 || to->nr_segs != runtime->channels)
                return -EINVAL;
        if (runtime->state == SNDRV_PCM_STATE_OPEN ||
            runtime->state == SNDRV_PCM_STATE_DISCONNECTED)
                return -EBADFD;
-       if (!iter_is_iovec(from))
+       if (!from->user_backed)
                return -EINVAL;
        if (from->nr_segs > 128 || from->nr_segs != runtime->channels ||
            !frame_aligned(runtime, iov->iov_len))