AMANDA FERGUSON and SACHIN RAVIKUMAR BRITISH Prime Minister Rishi Sunak was in Northern Ireland to sell his new deal with the European Union to ease post-Brexit trade, a measure he hopes will finally break the political deadlock in the province. Sunak is trying to secure the backing of all sides in Northern Ireland so he can reset relations with the EU - and the United States - without angering lawmakers in his own party and in Belfast who are most wedded to Brexit. His deal seeks to resolve the tensions caused by the Northern Ireland protocol, a complex agreement which set the…