MILAN (Reuters) – Shares in Porsche AG rose sharply above their initial public offering (IPO) price on their market debut in Frankfurt on Thursday as investors dumped shares in controlling investors Volkswagen and Porsche Holding. A Swiss-based equity fund manager said some investors that bought Volkswagen and Porsche Holding to play a potential IPO boom might be unwinding their positions and switching into Porsche AG, which was trading fairly closely to its IPO price. Porsche AG shares had risen as much as 5.2% compared to the IPO price of 82.5 euros by 0922 GMT, while Volkswagen and Porsche …