Add 16A8W support and tests for add operation on Ethos U55/U85

[Ninja91]

Stack from ghstack (oldest at bottom):

• -> Add 16A8W support and tests for add operation on Ethos U55/U85 #13790

Add 16A8W quantization support and comprehensive tests for the add operation in ExecutorTorch ARM backend targeting Ethos U55 and U85 NPUs.

This follows the pattern established for linear operations, extending int16 support to add operations with hardware-specific testing.

Changes:

• Add INT16 dtype validation support in op_add.py
• Add test_add_tensor_16a8w_tosa_INT test function with U55/U85 pipeline support
• Add U55 and U85 specific 16A8W tests with proper xfail decorators
• Fix U55/U85 test parameter usage (remove unsupported tosa_extensions, clean quantizer function calls)
• Update xfail reasons to consistent 'Vela compilation fails with Invalid arguments' pattern
• Remove redundant u55_config parameter from get_symmetric_a16w8_add_quantizer function
• Enable test_add.py in test targets configuration for both fbcode and xplat

The 16A8W configuration uses 16-bit activations with 8-bit weights, enabling higher precision for activations while maintaining weight efficiency on ARM Ethos NPUs.

Differential Revision: D81295079

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/13790

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

❌ 2 New Failures, 1 Pending

As of commit 396ffc9 with merge base 6208340 ():

NEW FAILURES - The following jobs have failed:

• pull / unittest / macos / macos-job (gh)
  backends/xnnpack/test/ops/test_sqrt.py::TestSqrt::test_fp16_sqrt
• pull / unittest-arm-backend-with-no-fvp (test_pytest_ops) / linux-job (gh)
  RuntimeError: Command docker exec -t e12aca30525e65c19e4b4f9d01e546530da0ba546fff23a3399d2630d161ead4 /exec failed with exit code 1

This comment was automatically generated by Dr. CI and updates every 15 minutes.

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D81295079

[github-actions]

This PR needs a release notes: label

If your change should be included in the release notes (i.e. would users of this library care about this change?), please use a label starting with release notes:. This helps us keep track and include your important work in the next release notes.

To add a label, you can comment to pytorchbot, for example
@pytorchbot label "release notes: none"

For more information, see
https://github.com/pytorch/pytorch/wiki/PyTorch-AutoLabel-Bot#why-categorize-for-release-notes-and-how-does-it-work.