By OKECHUKWU PEACE   The fear of dominance of MTN Group Ltd in the data service market is the real reason Emirates Telecommunications Group Co is suing its Nigerian competitor, Bloomberg reported. With the latest acquisition of Visafone Communications Ltd, MTN will become the biggest player with its unrestrained access to Visafone’s 800 megahertz of spectrum. Abu Dhabi-based Etisalat’s Nigeria unit said …