fix: remove duplicate desc declaration

dsv4/kernels/attention/fmha_sm100.cuh

@@ -138,7 +138,6 @@ __device__ __forceinline__ uint64_t make_umma_smem_desc_bf16(
     //
     // For now, use a simplified descriptor with raw byte addressing.
     // The descriptor format is documented in the PTX ISA for tcgen05.mma.
-    uint64_t desc = 0;
     // The UMMA descriptor packs: base_addr_16B | leading_dim_16B | stride_16B | flags
     // This is specific to the SM100 MMA descriptor format.
     // See: cutlass/include/cute/arch/mma_sm100_desc.hpp SmemDescriptor
@@ -156,7 +155,7 @@ __device__ __forceinline__ uint64_t make_umma_smem_desc_bf16(
     
     // For now, return a placeholder descriptor.
     // TODO: Properly construct using CUTLASS SmemDescriptor bitfield.
-    return desc;
+    return 0ULL;
 }
 
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