planning: optimize dp_st_boundary implemention.
planning: optimize dp_st_boundary implemention.

jinghaomiao/apollo,jinghaomiao/apollo,ApolloAuto/apollo,ApolloAuto/apollo,jinghaomiao/apollo,wanglei828/apollo,xiaoxq/apollo,ycool/apollo,wanglei828/apollo,jinghaomiao/apollo,ApolloAuto/apollo,xiaoxq/apollo,ycool/apollo,ycool/apollo,wanglei828/apollo,xiaoxq/apollo,ycool/apollo,wanglei828/apollo,jinghaomiao/apollo,ApolloAuto/apollo,xiaoxq/apollo,wanglei828/apollo,jinghaomiao/apollo,ApolloAuto/apollo,xiaoxq/apollo,ApolloAuto/apollo,wanglei828/apollo,ycool/apollo,xiaoxq/apollo,ycool/apollo