PROM princess or porn queen? This prom dress is so skimpy, even the designer's CEO wouldn't let his teenage daughter wear it. But the dangerously revealing gown, prominently advertised in Seventeen Prom, YM Prom and Teen Prom, and on sale in a Midtown shop, is a top seller for the company this season. "I was shocked when I first saw it, but now it's one of our top 20 dresses nationwide," says Nick Yeh, the CEO of Xcite, the Stafford, Texas, company that designed the dress and some 200 other styles this season. "I have a 15-year-old daughter and, no,...