Add intel_amx backend for Radix Attention for CPU (#6408)

Co-authored-by: Chunyuan WU <chunyuan.wu@intel.com>
Co-authored-by: Thien Tran <gau.nernst@yahoo.com.sg>

python/sglang/srt/utils.py

@@ -2225,3 +2225,21 @@ def bind_or_assign(target, source):
         return target
     else:
         return source
+
+
+def support_triton(backend: str) -> bool:
+    return backend not in ["torch_native", "intel_amx"]
+
+
+try:
+    import sgl_kernel
+
+    is_intel_amx_backend_available = hasattr(
+        torch.ops.sgl_kernel, "convert_weight_packed"
+    )
+except:
+    is_intel_amx_backend_available = False
+
+
+def cpu_has_amx_support():
+    return torch._C._cpu._is_amx_tile_supported() and is_intel_amx_backend_available