[PATCH v6] eal/x86: optimize memcpy of small sizes

[Varghese, Vipin]

[Public]

Hi @Morten Brørup, quick query in function `rte_mov17_to_32`

```
+       if (__rte_constant(n)) {
+               if (n == 16) {
+                       rte_mov16((uint8_t *)dst, (const uint8_t *)src);
+                       rte_mov1((uint8_t *)dst + 16, (const uint8_t *)src + 16);
+                       return dst;
+               }
+               if (n == 17) {
+                       rte_mov16((uint8_t *)dst, (const uint8_t *)src);
+                       rte_mov1((uint8_t *)dst + 16, (const uint8_t *)src + 16);
+                       return dst;
+               }
```

For `size 16` do we need to call ` rte_mov1((uint8_t *)dst + 16, (const uint8_t *)src + 16);`? Can you please help me understand the corner case for the same.