PR #10626: [XLA:CPU][oneDNN] Add a BF16 pattern for Softmax
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PR #10626: [XLA:CPU][oneDNN] Add a BF16 pattern for Softmax

Imported from GitHub PR https://github.com/openxla/xla/pull/10626

This PR:

1. Adds a pattern for BF16 softmax.
2. Adds a test to verify rewrite and execution result.
3. Skips BF16 matmul / softmax tests on machines that do not support BF16
Copybara import of the project:

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f0370a18eed1f2b47d8dc15470b970029726b0e8 by Akhil Goel <akhil.goel@intel.com>:

Add Softmax BF16 pattern and test

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62af424e4e74ddb7f64584aa3b05be761db956dc by Akhil Goel <akhil.goel@intel.com>:

Declare convert_instr identifier

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d030100ea87923582aa64cdcf0fac1464051288c by Akhil Goel <akhil.goel@intel.com>:

Fix formatting

Merging this change closes #10626

FUTURE_COPYBARA_INTEGRATE_REVIEW=https://github.com/openxla/xla/pull/10626 from Intel-tensorflow:akhil/bf16_softmax d030100ea87923582aa64cdcf0fac1464051288c
