Set GRF_mode==large for mxfp8 matmul tests

Author: HBN-MichalSzy

python/test/unit/language/test_matmul.py

@@ -1298,6 +1298,8 @@ def create_operand(dtype: str, size0: int, size1: int, k_dim: int, transpose: bo
         kernel_kwargs["matrix_instr_nonkdim"] = nonKDim
     if is_xpu() and (128, 256, 256) == (BLOCK_M, BLOCK_N, BLOCK_K) and not CONST_SCALE and not PACK_B_ALONG_K:
         kernel_kwargs["num_warps"] = 8
+    if is_xpu():
+        kernel_kwargs["grf_mode"] = "large"
     out = mxfp8_mxfp4_matmul[grid](a, b, output, a_scale, b_scale, M, N, K, stride_scale, a.stride(0), a.stride(1),
                                    b.stride(0), b.stride(1), output.stride(0), output.stride(1), not CONST_SCALE,
                                    dtype_converter[A_DATA_TYPE], dtype_converter[B_DATA_TYPE], BLOCK_M, BLOCK_N,