No, Jonathan Ive is the VP of Industrial Design and is not responsible for the iPhone user interface design.
This said, the software and hardware teams undoubtably spend many hours working together.
Scott Forstall leads the iPhone software team, and just like Mac OS X, many visual designers and interaction/usability experts contribute to the finished UI.
Both teams are overseen and directed by Steve Jobs. Ive and Forstall report directly to him.
Hope this helps.