Add definition for Menu.SubMenu (#14488)

Fix Menu.SubMenu props from any to real def

components/menu/SubMenu.tsx

@@ -3,7 +3,15 @@ import * as PropTypes from 'prop-types';
 import { SubMenu as RcSubMenu } from 'rc-menu';
 import classNames from 'classnames';
 
-class SubMenu extends React.Component<any, any> {
+export interface SubMenuProps {
+  rootPrefixCls?: string;
+  className?: string;
+  disabled?: boolean;
+  title?: React.ReactNode;
+  onTitleClick?: (key: string, domEvent?: Event) => void;
+}
+
+class SubMenu extends React.Component<SubMenuProps, any> {
   static contextTypes = {
     antdMenuTheme: PropTypes.string,
   };