By Stephen Nellis SAN FRANCISCO (Reuters) -Gaps in efforts by the U.S. and allies to restrict China's ability to manufacture advanced computing chips have allowed China to buy nearly $40 billion of sophisticated chipmaking gear, according to a bipartisan investigation by U.S. lawmakers. U.S. Democratic and Republican administrations have tried to restrict China's ability to make microchips, viewing the industry as crucial for national security. But inconsistencies in rules issued by the United States, J ...