[backport] Sync stream in ellpack format. (dmlc#10374) (dmlc#10391)

Author: trivialfis

src/data/ellpack_page_raw_format.cu

@@ -36,6 +36,7 @@ class EllpackPageRawFormat : public SparsePageFormat<EllpackPage> {
     if (!fi->Read(&impl->base_rowid)) {
       return false;
     }
+    dh::DefaultStream().Sync();
     return true;
   }