Yoshinobu Yamamoto earned his first MLB win Saturday after throwing five shutout innings on three hits and eight strikeouts in the Los Angeles Dodgers’ 4-1 victory over the Chicago Cubs. Making his third start in the big leagues, Yamamoto (1-1) loaded the bases in the first two innings but struck his way out of the jams before tossing three perfect innings in an 80-pitch outing at Wrigley Field, snapping the Cubs’ five-game winning streak. “I’m really happy,” said the 25-year-old Yamamoto, who in December penned the most valuable contract ever offered to a pitcher with a 12-year, $325 million …