By Foo Yun Chee BRUSSELS (Reuters) -Candy and snacks giant Mars' $36 billion bid to acquire Pringles maker Kellanova is set to clear a major hurdle by winning unconditional European Union antitrust approval, three people with direct knowledge of the matter said. The deal, among the biggest in the sector, would bring under one roof brands ranging from M&Ms, Snickers and Whiskas cat food to Pringles crisps, Pop-Tarts and Kellogg's cereals. It has already secured a green light without any conditions from U. ...