By Anita Komuves BUDAPEST (Reuters) – An hours-long blockade of a bridge in Budapest on Tuesday failed to derail the approval of a motion by Hungarian Prime Minister Viktor Orban’s government to increase the tax rate for hundreds of thousands of small firms. Protesters against the overhaul gathered at a main square outside parliament before marching to the nearby bridge over the River Danube, blocking traffic in both directions between the two sides of Budapest amid a heavy police presence. Nationalist Orban is facing his toughest challenge yet since taking power in a 2010 landslide, with infl…