By Lucia Mutikani WASHINGTON (Reuters) – U.S consumer prices fell for the first time in more than 2-1/2 years in December as gasoline and motor vehicles prices declined, offering hope that inflation was now on a sustained downward trend, though the labor market remains tight. Americans also got more relief at the supermarket last month, with the report from the Labor Department on Thursday showing food prices posting their smallest monthly increase since March 2021. But rents remained very high and utilities were more expensive. Cooling inflation could allow the Federal Reserve to further scal…