virtio-blk: fix comment for virtio_blk_rw_complete

Here should be submit_requests, there is no submit_merged_requests
function.
Signed-off-by: NYaowei Bai <baiyaowei@cmss.chinamobile.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

hw/block/virtio-blk.c

@@ -97,8 +97,8 @@ static void virtio_blk_rw_complete(void *opaque, int ret)
 
         if (req->qiov.nalloc != -1) {
             /* If nalloc is != 1 req->qiov is a local copy of the original
-             * external iovec. It was allocated in submit_merged_requests
-             * to be able to merge requests. */
+             * external iovec. It was allocated in submit_requests to be
+             * able to merge requests. */
             qemu_iovec_destroy(&req->qiov);
         }