[GPTQ] Add inversion fallback

[kylesayrs]

Purpose

• Given the increasing size of large language models (such as DeepSeek-R1 which contains 45034 linear layers), the likelihood that any of the hessian inversions will spontaneously fail is significant
• These changes cause the GPTQ algorithm to fall back to RTN for any layers which fail hessian inversion

Changes

• Implement fallback by setting hessian value to identity matrix if inversion fails

[github-actions]

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[brian-dellabetta]

cool!