Change to choice

The sequence element is changed to choice element with minOccurs="0" and
maxOccurs="unbounded" for supporting any order and any times sub
element. And maxOccurs of subelement is deleted because maxOccurs are
not needed.

Bug: 127435354
Test: m -j
Change-Id: I72866da5b2a8ac37d725f5b604dae37a06f30162