C2InterfaceHelper: fix split parameter handling

Bug: 160259947
Test: manual
Change-Id: I4cb9044db9174268b32b02bd5a74c82afe505953
diff --git a/media/codec2/vndk/util/C2InterfaceHelper.cpp b/media/codec2/vndk/util/C2InterfaceHelper.cpp
index 9eb52d2..19d2295 100644
--- a/media/codec2/vndk/util/C2InterfaceHelper.cpp
+++ b/media/codec2/vndk/util/C2InterfaceHelper.cpp
@@ -645,6 +645,7 @@
                     lateReadParams.emplace_back(p);
                     std::unique_ptr<C2Param> request(C2Param::CopyAsRequest(*p));
                     p = request.get();
+                    paramIx = p->index();
                     paramRequests.emplace_back(std::move(request));
                 }
             }