control: add more mpc control config pb comments.
control: add more mpc control config pb comments.

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