* Banks and carmakers jump, yen nudges towards 94 to the dollar * DeNa loses out as poor overseas performance highlighted By Sophie Knight TOKYO, Feb 18 (Reuters) - Japan's Nikkei share average jumped 2.3 percent in early trade on Monday, with exporters and banks leading the pack after the yen softened on the G20's decision not to single out Japan for undertaking policies that have weakened its currency. The Nikkei added 254.32 points to 11,429.15, with financials and real estat