[oneDNN] Check for bf16 support on CPU
This PR adds checks for BF16 since BF16 with oneDNN is not supported on AVX2 or earlier CPUs. The changes in remapper make sure that the fusions do not happen if oneDNN  is enabled and BF16 is not supported. The tests for fused ops are skipped in this case as well. The changes in layout pass make sure that the translation to MKL op does not happen for the same reason and the op falls back to Eigen.

Note: Changes in AMP pass are not needed as all oneDNN ops with the exception of fused ops are supported with Eigen and will fallback to Eigen on AVX2 machines