PR #12901: [ROCM] fixing gemm_rewriter subtest BF16GemmCodeGen
PR #12901: [ROCM] fixing gemm_rewriter subtest BF16GemmCodeGen

Imported from GitHub PR https://github.com/openxla/xla/pull/12901

This is a subtest fix for ROCM platform

@xla-rotation: would you please take a look?
Copybara import of the project:

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fe6147564252a291003f9dae1de504052a9296f1 by Pavel Emeliyanenko <pavel.emeliyanenko@amd.com>:

fixing gemm_rewriter subtest

Merging this change closes #12901

FUTURE_COPYBARA_INTEGRATE_REVIEW=https://github.com/openxla/xla/pull/12901 from ROCm:ci_gemm_rewrite_test_fix fe6147564252a291003f9dae1de504052a9296f1
