Arm backend: Fix U55 convolution dtype reject messages

[Sebastian-Larsson]

Report the actual unsupported input, weight, or bias dtype instead of the convolution node dtype when rejecting U55 convolution partitions.

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218 @mansnils @robell @rascani

[pytorch-bot]

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❌ 3 New Failures, 1 Unclassified Failure

As of commit b05828a with merge base d0a8dd6 ():

NEW FAILURES - The following jobs have failed:

• Cadence Build & Test / hifi-build / hifi4 (gh)
  Input required and not supplied: aws-region
• Cadence Build & Test / vision-build / vision (gh)
  Input required and not supplied: aws-region
• pull / unittest / linux / linux-job (gh)
  examples/models/test/test_export.py::ExportTest::test_efficient_sam_export_to_executorch

UNCLASSIFIED FAILURE - DrCI could not classify the following job because the workflow did not run on the merge base. The failure may be pre-existing on trunk or introduced by this PR:

• trunk / test-models-macos-cpu (mv3, portable) / macos-job (gh) (this job did not run on the merge base, so DrCI cannot tell whether the failure is pre-existing)
  ##[error]The operation was canceled.

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