Currently, gpu-to-llvm lowering only supports one async dependency on gpu.launc_func. More than 1 dependency results in failure. (https://github.com/llvm/llvm-project/blob/main/mlir/lib/Conversion/GPUCommon/GPUToLLVMConversion.cpp#L954).

Since, the gpu.launch_func itself does not employ the restriction, updating the gpu-to-llvm to handle more than 1 async dependency would provide a more robust solution.