NEW YORK / LONDON, March 19 : Germany's Elmos Semiconductor is exploring a sale as its founders consider exiting the business, according to three people familiar with the matter.   Elmos, which has a market value of around 2.3 billion euros ($2.5 billion), has hired Morgan Stanley to advise on the process, the people said, requesting anonymity because the deliberations are confidential. Elmos and Morgan Stanley declined to comment. The company has begun early-stage discussions with potential