By Oliver Hirt FRANKFURT (Reuters) -Credit Suisse is sounding out investors for fresh cash, two people familiar with the matter said, approaching them for the fourth time in roughly seven years as it attempts a radical overhaul of its investment bank. The bank started in recent weeks to speak to investors about the move, the people said. Various scenarios are under discussion for the investment bank, including the most drastic option of largely exiting the U.S. market, two sources said. It is unclear how keen investors are and interest may be dampened by the fact that the bank, which has strug…