[libclc] [libclc] Reduce include usage in OpenCL builtins (PR #146840)

[Wenju He via cfe-commits]

================
@@ -6,5 +6,12 @@
 //
 //===----------------------------------------------------------------------===//
 
+#ifndef __CLC_OPENCL_OPENCL_INTEGER_ABS_H__
----------------
wenju-he wrote:

```suggestion
#ifndef __CLC_OPENCL_INTEGER_ABS_H__
```
one OPENCL should be sufficient, right?

https://github.com/llvm/llvm-project/pull/146840