Adds issue reference to Split-KV disable comment

Documents the GitHub issue tracking the Split-KV bugs that led to temporarily disabling the feature. This provides better context for future developers about why the functionality is disabled and where to find related discussion.

Author: LoserCheems

csrc/flash_api.cpp

@@ -256,6 +256,7 @@ std::tuple<at::Tensor, at::Tensor> set_params_splitkv(
     }
 
     // Temporarily disable Split-KV, because some bugs are still being fixed.
+    // See: https://github.com/SmallDoges/flash-dmattn/issues/47
     // Regardless of how it is set externally, always set num_splits back to 1.
     // This is to avoid the extra memory overhead of Split-KV.
     params.num_splits = 1;