SSE2 cv::Mat::dot

```
dot::MatType_Length::(8SC1, 32)    0.002 ms 0.000 ms    6.07   
dot::MatType_Length::(8SC1, 64)    0.006 ms 0.001 ms    7.46   
dot::MatType_Length::(8SC1, 128)   0.024 ms 0.003 ms    7.82   
dot::MatType_Length::(8SC1, 256)   0.088 ms 0.012 ms    7.45   
dot::MatType_Length::(8SC1, 512)   0.305 ms 0.047 ms    6.51   
dot::MatType_Length::(8SC1, 1024)  1.216 ms 0.161 ms    7.57 
```