The federal agency that oversees the mortgage giants Fannie Mae and Freddie Mac is set to file suits against more than a dozen big banks, accusing them of misrepresenting the quality of mortgage securities they assembled and sold at the height of the housing bubble, and seeking billions of dollars in compensation. The Federal Housing Finance Agency suits, which are expected to be filed in the coming days in federal court, are aimed at Bank of America, JPMorgan Chase, Goldman Sachs and Deutsche Bank, among others, according to three individuals briefed on the matter.