Arm backend: fix meandim when dim = None

[Erik-Lundell]

This is a valid argument, but the pass did not support it.

cc @freddan80 @per @zingo @oscarandersson8218 @digantdesai

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/14883

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❗ 1 Active SEVs

There are 1 currently active SEVs. If your PR is affected, please view them below:

• Driver update on H100 and A100 instances

❌ 1 New Failure, 1 Unrelated Failure

As of commit 2ac76c2 with merge base 0b748bf ():

NEW FAILURE - The following job has failed:

• pull / test-samsung-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t d903709b83f4df9dc484cdc1aaf73793d0d259c106334459185f45b57fe61911 /exec failed with exit code 1

BROKEN TRUNK - The following job failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• Apple / build-demo-ios / macos-job (gh) (trunk failure)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 74

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[Erik-Lundell]

@pytorchbot cherry-pick --onto release/1.0 -c {regression,critical,fixnewfeature,docs,release,examples,testci}

[pytorch-bot]

❌ 🤖 pytorchbot command failed:

@pytorchbot cherry-pick: error: argument -c/--classification: invalid choice: '{regression,critical,fixnewfeature,docs,release,examples,testci}' (choose from 'regression', 'critical', 'fixnewfeature', 'docs', 'release')

usage: @pytorchbot cherry-pick --onto ONTO [--fixes FIXES] -c
                               {regression,critical,fixnewfeature,docs,release}

Try @pytorchbot --help for more info.

[mergennachin]

@pytorchbot cherry-pick --onto release/1.0 -c fixnewfeature

[pytorchbot]

Cherry picking #14883

The cherry pick PR is at #14895 and it is recommended to link a fixnewfeature cherry pick PR with an issue. The following tracker issues are updated:

• [v1.0.0] Release Tracker #14288 (comment)

Details for Dev Infra team

Raised by workflow job