[libclc] libclc: clspv: update gen_convert.cl for clspv (PR #66902)

[Kévin Petit via cfe-commits]

================
@@ -484,4 +536,8 @@ def generate_float_conversion(src, dst, size, mode, sat):
     for dst in float_types:
         for size in vector_sizes:
             for mode in rounding_modes:
+                # Do not generate "_rte" conversion for clspv as they are
+                # handle natively
----------------
kpet wrote:

```suggestion
                # handled natively
```

https://github.com/llvm/llvm-project/pull/66902