[MI35x] fix gfx950 build error

[yzhou103]

by adding i8gemm codegen to generate empty config map for gfx950

Motivation

Technical Details

Test Plan

Test Result

Submission Checklist

• Look over the contributing guidelines at https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.

[Copilot]

Pull Request Overview

This PR fixes a gfx950 build error by adding i8gemm codegen functionality that generates an empty config map when no CSV configuration files are found for gfx950, falling back to creating a placeholder configuration.

Key changes:

• Adds a new codegen.py script for gfx950 i8gemm kernel configuration generation
• Implements fallback logic to generate empty configuration maps when gfx950-specific CSV files are absent
• Generates C++ header files with kernel configuration structures and macros

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