What will Soviet leader Mikhail Gorbachev do between summit meetings and state dinners? Possibly what many Americans do in their spare time--go to the movies. Motion Picture Assn. of America President Jack Valenti said Tuesday that 35-millimeter prints of "Platoon," "Cry Freedom," "Nuts," "The Princess Bride" and a videocassette of "Top Gun" had been sent to the Soviet Embassy for Gorbachev's viewing in the embassy's viewing room during his visit. "The Soviets asked for 'Platoon' and 'Top Gun,' " Valenti said. "I didn't send them for propaganda purposes. I chose the rest for their differences." There was nothing unusual about the request, Valenti said. "The Soviets always come to me (for movies) any time an important Politburo member comes to Washington," Valenti said. Valenti--who will meet Gorbachev at a small reception later this week--said he told White House Chief of Staff Howard Baker that Gorbachev and his wife, Raisa, could tour movie studios, have a reception or whatever they wanted if they came to Hollywood.