virtio-rng: refactor probe error handling

Code like
	vi->vq = NULL;
	kfree(vi)
does not make sense.

Clean it up, use goto error labels for cleanup.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/char/hw_random/virtio-rng.c

@@ -105,8 +105,8 @@ static int probe_common(struct virtio_device *vdev)
 
 	vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL);
 	if (index < 0) {
-		kfree(vi);
-		return index;
+		err = index;
+		goto err_ida;
 	}
 	sprintf(vi->name, "virtio_rng.%d", index);
 	init_completion(&vi->have_data);
@@ -124,13 +124,16 @@ static int probe_common(struct virtio_device *vdev)
 	vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
 	if (IS_ERR(vi->vq)) {
 		err = PTR_ERR(vi->vq);
-		vi->vq = NULL;
-		kfree(vi);
-		ida_simple_remove(&rng_index_ida, index);
-		return err;
+		goto err_find;
 	}
 
 	return 0;
+
+err_find:
+	ida_simple_remove(&rng_index_ida, index);
+err_ida:
+	kfree(vi);
+	return err;
 }
 
 static void remove_common(struct virtio_device *vdev)