PR #12199: [XLA:GPU] only enable cudnn fmha dbias on hopper + cudnn 8.9.6
PR #12199: [XLA:GPU] only enable cudnn fmha dbias on hopper + cudnn 8.9.6

Imported from GitHub PR https://github.com/openxla/xla/pull/12199

Dbias requires hopper + cudnn 8.9.6, hence this PR.
Copybara import of the project:

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ba4d8f507b1bae75d249fae1bf3d84c4e57199fa by cjkkkk <ske@nvidia.com>:

init

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68978ddc378c6a5a891187a043fc2a696c45f478 by cjkkkk <ske@nvidia.com>:

fix rewriter test

Merging this change closes #12199

FUTURE_COPYBARA_INTEGRATE_REVIEW=https://github.com/openxla/xla/pull/12199 from Cjkkkk:enable_dbias_only_hopper_cudnn8.9.6 68978ddc378c6a5a891187a043fc2a696c45f478
