PHOENIX — Michael Morse broke a sixth-inning tie with his sixth home run of spring training, and the Seattle Mariners defeated the Oakland Athletics 6-5 Monday. Morse homered off starter A.J. Griffin for a 4-3 lead, and Dustin Ackley added an RBI single later in the inning against Ryan Cook. Ackley added another run-scoring single in the eighth off Pat Neshek. Right-hander Hisashi Iwakuma, one of the candidates to become the Mariners’ No. 2 spot behind Felix Hernandez, gave up three runs and six hits in five innings, including Derek Norris’ two-run homer. Oakland’s Coco Crisp leaped and reached over …