sycl: honor GGML_HINT_SRC0_IS_HADAMARD (#27298)

Kernel is a port of `ggml-cuda/fwht.cu`

(us/run, median):
```
m x n x k           GEMM      FWHT   speedup
64 x    1 x  64     10.20     2.93     3.48x
64 x 2048 x  64     10.75     2.71     3.97x
128 x    1 x 128    10.33     2.88     3.59x
128 x   32 x 128     9.20     2.77     3.33x
128 x 2048 x 128    16.46     2.76     5.95x
256 x    1 x 256    10.19     2.77     3.68x
256 x 2048 x 256    16.69     3.41     4.89x
512 x 2048 x 512    54.16    12.89     4.20x
```

ggml/src/ggml-sycl/fwht.hpp

@@ -0,0 +1,12 @@
+#ifndef GGML_SYCL_FWHT_HPP
+#define GGML_SYCL_FWHT_HPP
+
+#include "common.hpp"
+
+// Fast Walsh-Hadamard transform, the fast path for a MUL_MAT whose src0 ggml has
+// tagged GGML_HINT_SRC0_IS_HADAMARD. src0 is not read at all. Returns false if the
+// shape is not one this can serve, in which case the caller must fall through to the
+// ordinary mat-mul dispatch.
+bool ggml_sycl_op_fwht(ggml_backend_sycl_context & ctx, const ggml_tensor * src, ggml_tensor * dst);
+
+#endif  // GGML_SYCL_FWHT_HPP