SHANGHAI (Reuters) -Hua Hong Semiconductor, China's second-largest chip foundry, posted modest gains in its Shanghai debut on Monday, reflecting a weak market sentiment and investor caution amid mounting Sino-U. Hua Hong raised $3 billion in China's biggest public offering this year, joining a long queue of local chipmakers to tap the stock market to fund expansion as Beijing seeks self-sufficiency in an escalating technology war with Washington. Hua Hong will use most of the proceeds to boost capacity at a facility in Wuxi, in eastern Jiangsu province, according to the company's prospectus