By John Revill ZURICH, Dec 5 (Reuters) - Swiss companies plan to relocate some of their operations and production abroad to ​deal with the impact of U.S. tariffs, according to a ‌study by business association economiesuisse. It surveyed more than 400 companies before and after Switzerland ‌last month agreed a deal to reduce U.S. tariffs from 39% to 15%, with a quarter of the firms already having identified concrete steps they were taking. Nearly a third of those firms have decided ⁠to increase investmen ...