Refine and add new Rome models (#548)

[ROCm/rccl commit: 283dc86a73]

projects/rccl/tools/topo_expl/topo_expl.cpp

@@ -145,6 +145,8 @@ NodeModelDesc model_descs[] = {
   {4, "topo_8p1h_1.xml",        "4 nodes 8P1H Alt."},
   {1, "topo_8p1h_2.xml",        "single node 8P1H Alt."},
   {4, "topo_8p1h_3.xml",        "4 nodes 8P1H Alt."},
+  {1, "topo_8p1h_4.xml",        "Single node 8P1H Alt."},
+  {2, "topo_8p1h_4.xml",        "2 nodes 8P1H Alt."},
 };
 
 int main(int argc,char* argv[])