[libclc] libclc: Add uintptr_t overloads of atomic_fetch_add and sub (PR #185263)

[Wenju He via cfe-commits]

================
@@ -17,3 +17,9 @@
 
 #define __CLC_BODY <atomic_def.inc>
 #include <clc/math/gentype.inc>
+
----------------
wenju-he wrote:

this is generic file for all targets. Probably need to add guard to both files
```
#if defined(__opencl_c_atomic_order_seq_cst) && defined(__opencl_c_atomic_scope_device) && defined(_CLC_GENERIC_AS_SUPPORTED)
```

https://github.com/llvm/llvm-project/pull/185263