Dyn TS will add a new type of chan activation, which does not need a Channel
Mode IE. Incidentally, the dyn PDCH also doesn't need this IE if it opts for
sending a PDCH ACT instead. So it makes sense to compose the Channel Mode IE
only after the dynamic decisions are done.
Change-Id: I66d88ad6a4ae7bee1e552960fd4e92aff953125c