In at least the case of mu=1, min_rxtxtime=2 and DDDSU with no UL
symbols (for ULSCH) in the mixed slot, the current state of code does
not allow a UE to attach. This is because at mu=1, Msg3 is k2+delta,
where k2=min_rxtxtime and delta(mu)=3.
Prior, this special case was handled because we had a dedicated Msg3
TDA, which in most cases is not necessary (because the mixed slot
allocates the DCI, and the following mixed slot has the UL grant). Add
code that tries to ensure that we only add the Msg3 TDA in cases when we
need it.
Fixes: 961a646dc7 ("Remove dedicated Msg3 TDA")
Robert Schmidt
bd6180e362