As PPs have said, yes, there are irons and ironing boards available in the laundry rooms on each deck. But…
Agree with lorimay - great advice as usual. The prices for laundry (ranging from just pressing through full dry cleaning) are (surprisingly) reasonable. We don't save up for a cruise to be spending any time doing laundry. For a small expense, we spend that time on deck relaxing. We often send out whatever needs pressing the first night, have it back the next day, and are set for the cruise.