[AMD] Leverage MLIR error report infra in more places (triton-lang#5719)

This is a minor change, when implementing PR triton-lang#5549 I used:
```rewriter.notifyMatchFailure``` in place of ```return failure();``` as
per suggestions to leverage MLIR infra for errors.

We should probably be consistent throughout the file and use the MLIR
infra for the other buffer ops.

Author: SamGinzburg

third_party/amd/lib/TritonAMDGPUToLLVM/LoadStoreOpToLLVM.cpp

@@ -581,15 +581,17 @@ struct BufferAtomicRMWOpConversion
     switch (memScope) {
     // System scope is not supported yet
     case MemSyncScope::SYSTEM:
-      return failure();
+      return rewriter.notifyMatchFailure(
+          op, "System memory scope is not supported for Buffer Atomic RMW");
     case MemSyncScope::GPU:
       scopeStr = "agent";
       break;
     case MemSyncScope::CTA:
       scopeStr = "workgroup";
       break;
     default:
-      return failure();
+      return rewriter.notifyMatchFailure(
+          op, "Unsupported memory scope for Buffer Atomic RMW");
     }
 
     StringAttr scope = mlir::StringAttr::get(loc.getContext(), scopeStr);
@@ -815,7 +817,7 @@ struct AtomicCASOpConversion
     auto scope = op.getScope();
     auto scopeStr = getAMDGPUMemScopeStr(scope);
     if (!scopeStr)
-      return failure();
+      return rewriter.notifyMatchFailure(op, "Unknown AMDGPU memory scope");
 
     // deal with tensor or scalar
     auto valueTy = op.getResult().getType();
@@ -1143,7 +1145,7 @@ struct AtomicRMWOpConversion
 
     auto scopeStr = getAMDGPUMemScopeStr(scope);
     if (!scopeStr)
-      return failure();
+      return rewriter.notifyMatchFailure(op, "Unknown AMDGPU memory scope");
 
     auto vecTy = vec_ty(valueElemTy, vec);
     auto retType = vec == 1 ? valueElemTy : vecTy;

third_party/amd/lib/TritonAMDGPUTransforms/ConvertToBufferOps.cpp

@@ -422,8 +422,9 @@ struct ConvertTritonLoadToBufferLoad
       rewriter.replaceOp(op, bufferLoadOp);
       return success();
     }
+
     LDBG("Failed to convert: " << op);
-    return failure();
+    return rewriter.notifyMatchFailure(op, "Failed to convert LoadOp");
   }
 
 private:
@@ -462,7 +463,7 @@ struct ConvertTritonStoreToBufferStore
       return success();
     }
     LDBG("Failed to convert: " << op);
-    return failure();
+    return rewriter.notifyMatchFailure(op, "Failed to convert StoreOp");
   }
 
 private: