[ROCm][Bugfix] Disable hip sampler to fix deepseek's accuracy issue on ROCm (#32413)

Signed-off-by: ganyi <ygan@amd.com>

vllm/v1/sample/ops/topk_topp_sampler.py

@@ -174,6 +174,8 @@ class TopKTopPSampler(nn.Module):
         k: torch.Tensor | None,
         p: torch.Tensor | None,
     ) -> tuple[torch.Tensor, torch.Tensor | None]:
+        # FIXME: Fix aiter_sampler's accuracy issue and remove this flag
+        DISABLE_AITER_SAMPLER = True
         """Optimized ROCm/aiter path (same structure as forward_cuda)."""
         if (k is None and p is None) or generators:
             if generators:
@@ -186,6 +188,8 @@ class TopKTopPSampler(nn.Module):
             "processed_logits",
             "processed_logprobs",
         ), "aiter sampler does not support returning logits/logprobs."
+        if DISABLE_AITER_SAMPLER:
+            return self.forward_native(logits, generators, k, p)
         return self.aiter_sample(logits, k, p, generators), None
 
     def aiter_sample(