Before this commit, the DMRS_UplinkConfig was stored in a separate
DMRS-related structure, although it is always referenced in the
PUSCHConfig of the current UL BWP.

Through certain code paths (e.g., retransmission), it could happen that
an old DMRS_UplinkConfig was accessed that was freed (through new
CellGroupConfig).

In this commit, we always look up the DMRS_UplinkConfig in the current
PUSCH config, which should always be up to date.