By Jason Lange and Lisa Lambert WASHINGTON (Reuters) - The Federal Reserve Board's top bank regulator said on Friday he would resign, giving a boost to President Donald Trump's plans to ease reforms put in place after the 2007-09 financial crisis. Daniel Tarullo, a strong regulator who was dovish on monetary policy in his seven years on the board, said in his resignation letter to Trump he would leave the U.S. central bank on or around April 5. With his resignation, Trump will have three positions to fill on the Fed's Board of Governors, which at full strength has seven members.