By Jan Schwartz, Emma-Victoria Farr and Lucy Raitano HAMBURG/FRANKFURT/LONDON (Reuters) -Volkswagen’s supervisory board is due to meet on Sunday to move forward with the IPO of its Porsche brand, which will comprise 911 million shares in a nod to its most famous model, two sources close to matter said. Details on the price range, valuation and confirmed cornerstone investors are likely to be announced after the meeting, a third source said. The 911 million Porsche AG shares will be divided into 455.5 million preferred shares and 455.5 million ordinary shares, according to the website for the s…