[libclc] [libclc] Reduce bithacking in CLC frexp (PR #129871)

[Romaric Jodin via cfe-commits]

rjodinchr wrote:

The following patch is fixing the issue on my side:
```
-   __CLC_INTN is_inf_nan_or_zero =
-      x == __CLC_FP_LIT(0.0) || __clc_isinf(x) || __clc_isnan(x);
+   __CLC_INTN is_inf_nan_or_zero =
+      ai == (__CLC_INTN)0 || e == (__CLC_INTN)129 || __clc_isinf(x) || __clc_isnan(x);
```


https://github.com/llvm/llvm-project/pull/129871