[rocm-libraries] ROCm/rocm-libraries#8554 (commit be9af54)

refactor(ck): mx gemm kernel unification

## Motivation

CK tile currently has two separate MX GEMM kernels for gfx950 and
gfx1250. This pull request refactors and modernizes the MX GEMM kernel
and example to use new scale tensor handling, improved kernel argument
structures, and updated pipeline and kernel APIs. The changes simplify
the interface and improve type safety.

JIRA ID ROCM-26313

## Technical Details

- Add support for gfx950 in MX GEMM kernel for gfx1250 and remove unused
kernel
 - Unify comp async pipeline for GEMM and MX GEMM
 - Unify eight waves pipeline for GEMM and MX GEMM
 - Move preshuffle MX GEMM pipeline to gemm ops and remove gemm_mx ops
 - Unify testing framework for MX GEMM
 - Add gfx950 tests for grouped MX GEMM

## Test Plan

 - `test_mx_gemm_async.cpp` for MX GEMM on gfx950
 - `test_mx_grouped_gemm_comp_async.cpp` for grouped MX GEMM on gfx950

## Submission Checklist

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

include/ck_tile/core/tensor/null_tensor.hpp

@@ -3,10 +3,28 @@
 
 #pragma once
 
+#include "ck_tile/core/utility/type_traits.hpp"
+
 namespace ck_tile {
 
 struct null_tensor
 {
 };
 
+// utility to check if this is a Null Tensor
+namespace impl {
+template <typename>
+struct is_null_tensor : public std::false_type
+{
+};
+
+template <>
+struct is_null_tensor<null_tensor> : public std::true_type
+{
+};
+} // namespace impl
+
+template <typename T>
+constexpr bool is_null_tensor_v = impl::is_null_tensor<remove_cvref_t<T>>::value;
+
 } // namespace ck_tile