HIP: Cleanup hipification header (#15285)
add expicit conversion operator to support older versions of rocm
Switch over to hip_bf16 from legacy hip_bfloat16
Simplify RDNA3 define
Reduce swap over of new hipblas api to rocm 6.5 as this version is used for rocm 7.0 previews
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Co-authored-by: Johannes Gäßler <johannesg@5d6.de>
