Similarly to previous patch this is preparatory non-functional change to
support multicell configurations.

Previously the number of transmitted transport blocks was passed around
as separate argument but with multiple cells each cell will have its own
information about how many TB were transmitted/received and we will need
to maintain those .tx and .retx in per-cell data structure.

Start preparing to that by moving .tx and .retx to be tracked in UE
transmission state instead of being passed around separately.

No support for multicell yet - only preparatory non-functional changes currently.