Update mixr-gemm-gemm tests for unsupported arch

[justinrosner]

Motivation

This PR addresses the issue identified in Navi2X LIT tests: https://github.com/ROCm/rocMLIR-internal/issues/1976

Technical Details

The lit.local.cfg that was added for mixr-gemm-gemm tests (found here: mlir/test/fusion/e2e/mixr-gemm-gemm/lit.local.cfg) wasn't properly being picked up by the LIT test infrastructure. This was leading to the config.unsupported not being run, and the two tests mentioned in the issue failing. The fix for this is to update mlir/test/fusion/e2e/lit.local.cfg so that we are using config.excludes to not run the entire directory of mixr-gemm-gemm tests.

Test Plan

• LIT tests on Navi2X
• LIT tests on the CI

Test Result

• LIT tests on Navi2X
• LIT tests on the CI

Submission Checklist

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

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1968      +/-   ##
===========================================
+ Coverage    79.50%   79.62%   +0.11%     
===========================================
  Files          100      102       +2     
  Lines        31016    31910     +894     
  Branches      4819     5047     +228     
===========================================
+ Hits         24659    25406     +747     
- Misses        4245     4312      +67     
- Partials      2112     2192      +80     

Flag	Coverage Δ
mfma	79.62% <ø> (+0.11%)	⬆️

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