TWO CHEERS: It will be business as usual tonight at Cheers--the Simi Valley nightspot, not the television show. As "Cheers" airs its final episode (F1), the bar that borrowed its name may not even tune in. "If somebody wants to watch it, we'll show the show," owner Mark Krumholz said. . . . He predicts the bar's clientele will skip the televised repartee in favor of his regular Thursday-night fare: a battle of the bands.