[CPU][BugFix] Fix loading of w8a8int models with bias (#33582)

Signed-off-by: Fadi Arafeh <fadi.arafeh@arm.com>

vllm/model_executor/layers/quantization/kernels/mixed_precision/dynamic_4bit.py

@@ -86,9 +86,14 @@ class Dynamic4bitLinearKernel(MPLinearKernel):
             )  # Float32 & Bfloat16 variants requires float32 scales
             scales = scales.view(-1, 1)  # Channel-wise scales
             if layer.bias is not None:
-                layer.bias = layer.bias.to(
-                    torch.float32
-                )  # Float32 & Bfloat16 variants requires float32 bias
+                # Float32 & Bfloat16 variants requires float32 bias
+                replace_parameter(
+                    layer,
+                    "bias",
+                    torch.nn.Parameter(
+                        layer.bias.to(torch.float32), requires_grad=False
+                    ),
+                )
         else:
             # KleidiAI kernel requires bfloat16 scales with groupwise scheme
             scales = scales.to(torch.bfloat16)