Add gfx908 VM model (#418)

[ROCm/rccl commit: 5f15ed6e3e]

projects/rccl/tools/scripts/topo_val.sh

@@ -21,7 +21,7 @@
 
 DIR="$(cd -P "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 
-for i in {0..54}
+for i in {0..55}
 do
 	if [[ $i -eq 50 ]] || [[ $i -eq 51 ]]
 	then