wedge800bact: platform: Switch MCB_PWRBRK_MONITOR to tda38640

[brandonchuang]

Pre-submission checklist

• I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running pip install -r requirements-dev.txt && pre-commit install
• pre-commit run
  $ pre-commit run --files fboss/platform/configs/wedge800bact/platform_manager.json fboss/platform/configs/wedge800bact/sensor_service.json
  clang-format.........................................(no files to check)Skipped
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  shfmt................................................(no files to check)Skipped
  trim trailing whitespace.................................................Passed
  fix end of files.........................................................Passed
  check yaml...........................................(no files to check)Skipped
  check json...............................................................Passed
  check for merge conflicts................................................Passed
  ruff check...........................................(no files to check)Skipped

Summary:

Update MCB_PWRBRK_MONITOR to use the tda38640 PMBus driver instead of xdpe15284, and align the sensor_service sysfs paths accordingly.

Based on vendor recommendation, tda38640 is a better fit for the power brick Q54SW120A7 because:

• Q54SW120A7 only operates on page 0.
• tda38640 is designed as a single-page PMBus device.
• Using a single-page driver provides a more stable and consistent integration with the hardware behavior.

Changes:

• platform_manager.json
  • Update MCB_PWRBRK_MONITOR kernelDeviceName from xdpe15284 to tda38640.
• sensor_service.json
  • Update VOUT sensor path from in3_input to in2_input.
  • Update IOUT sensor path from curr3_input to curr2_input.

Test Plan:

• Compilation and configuration validation completed successfully.
• On Wedge800BACT device:
  • platform_manager starts and runs normally.
    platform_manager.log
  • sensor_service starts normally and all sensors are correctly discovered.
    sensor_service.log
  • sensor_service_client: all test cases passed.
    sensor_service_client.log
• Executed platform_manager_hw_test and sensor_service_hw_test; all test cases passed.
  platform_manager_hw_test.log
  sensor_service_hw_test.log