(Adds background on China-U.S. IPO clampdown) Sept 9 (Reuters) - China's largest online audio platform Ximalaya said on Thursday it had decided not to proceed with its plans for an initial public offering (IPO) in the United States. The move comes after Reuters reported in May that China was pressing Ximalaya to drop its plans to list in the United States and go for Hong Kong instead, showing how authorities are seeking to further tighten their grip over private media and internet businesses. Medical data group LinkDoc Technology Ltd in July became the first Chinese company to shelve plans for...