By Caroline Valetkevitch NEW YORK (Reuters) – U.S. stocks were mostly higher in choppy trading while the dollar fell against the Japanese yen on Wednesday after the U.S. Federal Reserve announced a three-quarters of a percentage point interest rate hike but signaled that smaller increases may be coming. U.S. Treasury yields extended their decline after the announcement. The U.S. central bank announced the rate hike, as expected, following its two-day meeting. But it suggested that future increases in borrowing costs could be made in smaller steps. The Fed has been aggressively raising rates in…