tune_gemm: use correct output option for rocprofv3

[matthiasdiener]

Without this, rocprofv3 (at least some versions of it) does not produce a csv output as required in the later stages of tune_gemm.

Tested with:

# rocprofv3 --version
             version: 1.0.0
        git_revision: 18af6a58b74558c91ba09376d86d2401da2cf76f
        library_arch: x86_64-linux-gnu
         system_name: Linux
    system_processor: x86_64
      system_version: 5.15.0-151-generic
         compiler_id: GNU
    compiler_version: 11.4.0
        rocm_version: 7.0.0

Also tested with rocprofv3 from ROCm 6.4.4 (rocm/pytorch:rocm6.4.4_ubuntu24.04_py3.12_pytorch_release_2.7.1 docker image).

---

Sample error message without this PR:

# ./tune_gemm.py --gemm_size_file t.yaml
Tuning 1 gemm sizes starts at: 2025-10-03 15:41:40.953138
SIZE: 8192 8192 8192 TN nConfigs: 6 Traceback (most recent call last):
  File "/dockerx/triton/python/perf-kernels/tools/tune_gemm/./tune_gemm.py", line 725, in <module>
    sys.exit(main())
             ^^^^^^
  File "/dockerx/triton/python/perf-kernels/tools/tune_gemm/./tune_gemm.py", line 655, in main
    minTime, bestConfig, compile_time, profile_time, post_time = tune_gemm_config(
                                                                 ^^^^^^^^^^^^^^^^^
  File "/dockerx/triton/python/perf-kernels/tools/tune_gemm/./tune_gemm.py", line 255, in tune_gemm_config
    df_prof = [pd.read_csv(f"{get_output_dir()}/{i}_kernel_trace.csv") for i in range(jobs)]
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/venv/lib/python3.12/site-packages/pandas/io/parsers/readers.py", line 1026, in read_csv
    return _read(filepath_or_buffer, kwds)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/venv/lib/python3.12/site-packages/pandas/io/parsers/readers.py", line 620, in _read
    parser = TextFileReader(filepath_or_buffer, **kwds)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/venv/lib/python3.12/site-packages/pandas/io/parsers/readers.py", line 1620, in __init__
    self._engine = self._make_engine(f, self.engine)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/venv/lib/python3.12/site-packages/pandas/io/parsers/readers.py", line 1880, in _make_engine
    self.handles = get_handle(
                   ^^^^^^^^^^^
  File "/opt/venv/lib/python3.12/site-packages/pandas/io/common.py", line 873, in get_handle
    handle = open(
             ^^^^^
FileNotFoundError: [Errno 2] No such file or directory: '/dockerx/triton/python/perf-kernels/tools/tune_gemm/output/0_kernel_trace.csv'

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