With markup of GSE reform legislation tentatively scheduled for next week in the Senate, Federal Reserve Chairman Alan Greenspan continued to press lawmakers to effectively force Fannie Mae and Freddie Mac to slim down their retained mortgage investment portfolios. In separate hearings in the House and Senate banking committees this week, Greenspan sharply criticized the government-sponsored enterprise reform bill that’s treading water in the House. “No bill would be better” than the House bill, he…