In --do-ra mode, calculate_preferred_dl_tda() would be called without a
BWP. Then, get_searchspace() would search in the scc, leading to a
segfault. Therefore, don't call calculate_preferred_dl_tda() in do-ra
mode.

In F1, the time until the serving cell config comes from CU can be
longer than when we want to schedule a particular UE. Then, if we don't
configure the default number of HARQ processes, we can have a segfault.

In this commit, we initially configure 8 HARQ processes. When we get the
right number from RRC, we reconfigure.

- this will be later used to prioritise the LCs