tools/virtio: remove virtqueue_add_buf() from tests.

Make the rest of the paths use virtqueue_add_sgs or add_outbuf.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/tools/virtio/virtio_test.c b/tools/virtio/virtio_test.c
index 814ae80..da7a195 100644
--- a/tools/virtio/virtio_test.c
+++ b/tools/virtio/virtio_test.c
@@ -166,9 +166,9 @@
 		do {
 			if (started < bufs) {
 				sg_init_one(&sl, dev->buf, dev->buf_size);
-				r = virtqueue_add_buf(vq->vq, &sl, 1, 0,
-						      dev->buf + started,
-						      GFP_ATOMIC);
+				r = virtqueue_add_outbuf(vq->vq, &sl, 1,
+							 dev->buf + started,
+							 GFP_ATOMIC);
 				if (likely(r == 0)) {
 					++started;
 					virtqueue_kick(vq->vq);