Add another Rome model (#431)

tools/topo_expl/topo_expl.cpp

@@ -127,6 +127,7 @@ NodeModelDesc model_descs[] = {
   {1, "topo_8p_rome_vm1.xml",   "single node 8 gfx908 Rome VM"},
   {1, "topo_16p1h.xml",         "single node 16P1H"},
   {4, "topo_8p_rome_4n_2.xml",  "4 nodes 8 gfx908 Rome 4 NICs NPS=4 Alt. Model"},
+  {1, "topo_8p_90a_1.xml",      "single node gfx90a Alt. Model"},
 };
 
 int main(int argc,char* argv[])