By Astrid Wendlandt PARIS (Reuters) – Renzo Rosso, the founder of Diesel, says competition for hot designers is now as intense as for football stars, as shown by the speed at which big luxury groups such as LVMH are investing in promising new fashion names. "Fashion is like soccer, only champions make a difference," said the tattooed 58-year-old entrepreneur as he sat in the showroom of one of his brands, Maison Martin Margiela, in a converted 19th century convent in Paris. Earlier this month, two fledgling British fashion brands Rosso had been following for more than two years, J.W. …