[libclc] libclc: Fix missing overloads for atomic_fetch_add/sub (PR #188478)

[Wenju He via cfe-commits]

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@@ -27,12 +27,24 @@ atomic_fetch_add(volatile __local atomic_uintptr_t *p, ptrdiff_t v) {
                                    __ATOMIC_SEQ_CST, __MEMORY_SCOPE_DEVICE);
 }
 
+_CLC_OVERLOAD _CLC_DEF uintptr_t atomic_fetch_add(
+    volatile __local atomic_uintptr_t *p, ptrdiff_t v, memory_order order) {
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wenju-he wrote:

this variant don't need __opencl_c_atomic_order_seq_cst guard at line 21

https://github.com/llvm/llvm-project/pull/188478