Add new Rome model (#535)

[ROCm/rccl commit: ba4c165bf3]

projects/rccl/tools/topo_expl/topo_expl.cpp

@@ -142,6 +142,7 @@ NodeModelDesc model_descs[] = {
   {4, "topo_8p1h_n1.xml",       "4 nodes 8P1H"},
   {1, "topo_8p1h_1.xml",        "single node 8P1H Alt."},
   {4, "topo_8p1h_1.xml",        "4 nodes 8P1H Alt."},
+  {1, "topo_8p1h_2.xml",        "single node 8P1H Alt."},
 };
 
 int main(int argc,char* argv[])