(Adds company news items) LONDON, Sept 25 (Reuters) - European stocks were seen opening higher on Friday, although the region's major indexes could still end the week with a loss following blows dealt to the market this week by an emissions test debacle at Volkswagen and new signs of a slowdown in China. The prospect of a U.S interest rate rise has also weighed on equity markets, and Federal Reserve head Janet Yellen said late on Thursday that she expects the U.S. central bank to begi