[rocm-libraries] ROCm/rocm-libraries#7935 (commit 5c96097)

[CK] Allow skipping split-K C-buffer zero-init in
 xdl_cshuffle blockscale GEMM (#7935)

Add a `skip_zero_init` flag (default false) to the Problem/Argument of
the xdl_cshuffle block-scale GEMM device ops (multiple_d ab_scale and
blockscale b-preshuffle). When the flag is set, the device invoker skips
the internal hipMemsetAsync that zeroes p_c_grid before the KBatch > 1
split-K atomic-accumulation path. The flag is declared on the gridwise
Problem struct (inherited by Argument), so it is visible on both the
rotating-cache (arg_) and the normal (arg) launch paths in each device
op.

Why: callers that already pre-zero the output buffer otherwise pay for a
redundant device-wide memset before split-K atomic accumulation. Gating
the memset behind an opt-in flag lets such callers avoid the duplicate
work. Because the flag defaults to false, every existing call site is
unaffected and the observable behavior is unchanged.

## Motivation

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## Technical Details

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## Test Plan

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## Test Result

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## Submission Checklist

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

Co-authored-by: Cursor <cursoragent@cursor.com>