LOS ANGELES (Reuters) - Rihanna is returning to "American Idol." The "Rude Boy" singer will perform on the two-hour "Idol" season finale on May 23. The songbird will perform her recent hit "Where Have You Been." Rihanna (full name: Robyn Rihanna Fenty) has appeared twice before on the show. In April 2010, she performed her song "Rockstar 101," and returned the following April to belt out her song "California King Bed." As season 11 winds to a close, other guest performers are also being brought aboard. On the May 10 results show, "Idol" judge Jennifer Lopez will perform her single "Dance ...