Refine control message comments

Author: Cuda-Chen

virtio-snd.c

@@ -724,13 +724,12 @@ static int virtio_snd_desc_handler(virtio_snd_state_t *vsnd,
                                    uint32_t desc_idx,
                                    uint32_t *plen)
 {
-    /* virtio-snd command uses at most 3 virtqueue descriptors, where
+    /* A control message uses at most 3 virtqueue descriptors, where
      * the first descriptor contains:
-     *   struct virtio_snd_hdr hdr (for request)
+     *   struct virtio_snd_hdr hdr
      * the second descriptors contains:
-     *   struct virtio_snd_hdr hdr (for response)
-     * if needed, the third descriptors contains:
-     *   (response payload structure)
+     *   struct virtio_snd_hdr hdr
+     * if needed, the third descriptors contains the response payload structure.
      */
     struct virtq_desc vq_desc[VSND_DESC_CNT];