[rocm-libraries] ROCm/rocm-libraries#4883 (commit 56347bb)

[CK] Disable test_fmha_fwd_fp8fp16 on gfx90a by default. (#4883)

## Motivation

Since gfx90a has no native support for FP8 datatype, all FP8 tests
should be disabled there by default.

## Technical Details

The test_fmha_fwd_fp8fp16 is the last failing test in CK on gfx90a with
staging compiler.

## Test Plan

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## Test Result

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## Submission Checklist

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