[Hardware][AMD][Bugfix] Fix PTPC FP8 quantization

[mawong-amd]

Purpose

Fixes PTPC FP8 quantization and thus AMD Quantization Tests after the refactoring done in #32189. PTPCFP8LinearMethod should now inherit from FP8OnlineLinearMethod rather than FP8LinearMethod.

Test Plan

pytest -sv quantization/test_ptpc_fp8.py
The above is implicitly run as part of AMD CI's Quantization Tests group.

Test Result

The test and test group both pass.

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[gemini-code-assist]

Code Review

This pull request correctly fixes a bug in the PTPC FP8 quantization implementation. By changing the base class of PTPCFp8LinearMethod from Fp8LinearMethod to Fp8OnlineLinearMethod, the method now correctly inherits the behavior for online quantization, which is its intended purpose. This aligns with the fact that PTPC performs dynamic, on-the-fly quantization of weights rather than loading pre-quantized checkpoints. The change is logical, well-contained, and directly addresses the issue described. I find no issues with this correction.

[mawong-amd]

Closing since PTPC FP8 is being deprecated soon: #32700