[clang] [clang][AMDGPU] Clean-up handling of named barrier type (PR #207687)

[Pierre van Houtryve via cfe-commits]

================
@@ -68,6 +68,9 @@ enum class LangAS : unsigned {
   // Wasm specific address spaces.
   wasm_funcref,
 
+  // HIP-specific address spaces
+  hip_barrier,
----------------
Pierre-vh wrote:

I will rename it to `amdgpu_barrier`

https://github.com/llvm/llvm-project/pull/207687