By Amanda Ferguson BALLYNAHINCH, Northern Ireland (Reuters) – The leader of Northern Ireland’s Democratic Unionist Party (DUP) said it had reached a deal with the British government on the operation of post-Brexit trade rules that would allow it to return to the region’s power-sharing government. Northern Ireland has been without a devolved government for almost two years after the DUP walked out in protest over the trade rules, which it said created barriers with the rest of the United Kingdom and undermined Northern Ireland’s place in it. A return to government by the region’s largest pro-Br…