By Charlie Devereux and Corina Pons MADRID (Reuters) – Madrid has broken ground on a new business district three decades in the planning, but with similar zones in London, Paris and New York struggling as more people work from home, critics see a risk the project could become a giant white elephant. With a first phase due to be completed by 2035, Madrid Nuevo Norte (MNN) will add 1.6 million square metres (17 million square feet) of office space to the capital, including Spain’s tallest skyscraper. The plans also include 10,500 new homes and a large park, while Chamartin station will be upgrad…