By Lawrence Delevingne (Reuters) -U.S. stocks were mostly flat on Monday, the dollar weakened and U.S. government bond yields fell as investors weighed mixed messages on inflation and how aggressive the Federal Reserve will be in combating it. On Wall Street, The Dow Jones Industrial Average was virtually flat, while the S&P 500 lost 0.2% and the Nasdaq Composite dropped 0.2% Of note was Nvidia Corp, whose stock declined around 8% after the chip designer warned on Monday that its second-quarter revenue would drop by 19% from the prior quarter on weakness in its gaming business. The broad Euro …