[DeepSeek v3.2] Remove unnecessary syncwarps (#31047)

Signed-off-by: Matthew Bonanni <mbonanni@redhat.com>

csrc/cache_kernels.cu

@@ -451,9 +451,6 @@ __global__ void indexer_k_quant_and_cache_kernel(
   for (int i = 0; i < VEC_SIZE; i++) {
     amax = fmaxf(amax, fabsf(float(k_val_ptr[i])));
   }
-#ifndef USE_ROCM
-  __syncwarp();
-#endif
 
   // Reduced amax
   for (int mask = 16; mask > 0; mask /= 2) {
@@ -463,9 +460,7 @@ __global__ void indexer_k_quant_and_cache_kernel(
     amax = fmaxf(amax, __shfl_xor_sync(unsigned(-1), amax, mask));
 #endif
   }
-#ifndef USE_ROCM
-  __syncwarp();
-#endif
+
 #if defined(__gfx942__)
   float scale = fmaxf(amax, 1e-4) / 224.0f;
 #else