[rocm-libraries] ROCm/rocm-libraries#5388 (commit 45583bd)

[CK_TILE][FMHA] Improve precision of mxfp4 FMHA with fp6 for matrix P (#5388)

## Motivation

Improve precision of mxfp4 without performance penalties.

## Technical Details

Since performance of scale MFMAs is the same when neither A nor B is
fp8/bf8, it is possible to use fp6 x fp4 instead of fp4 x fp4 for the
second GEMM, while types of Q, K, V stay the same.
This allows to improve overall precision significantly because fp6 has
32 non-negative values used for P quantization compared to just 8 values
for fp4.

It was found that there is a compiler bug with
`__builtin_amdgcn_cvt_scalef32_2xpk16_fp6_f32` (described in
LCOMPILER-561) but a workaround seems to fix all failing instances.

## Test Plan

```
ninja test_ck_tile_fmha_fwd_mxfp4 && bin/test_ck_tile_fmha_fwd_mxfp4
```

## Test Result

The tests must pass.

## Submission Checklist

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