Southern California has got Mayo, as in O.J. Mayo, and the Trojans showed off their star recruit when he and the rest of the team scrimmaged for fans Friday night. The Midnight Madness session kicked off the start of practice for the Trojans, who open the season Nov. 10, at home against Mercer. Introduced next-to-last, Mayo jogged onto the court with the index and middle fingers on both hands…