I fear I might suffer from a certain cultural disconnect reviewing Halkawt Mustafa’s “El Clásico,” the winner of Tribeca’s 2016 award for Best Cinematography in an International Narrative Feature Film. The film hinges on a presumption that football, or “soccer” as it’s known here in the States, is a powerful enough force that the goodwill of one of its players can literally be enough to dissuade deeply-felt prejudices