fill_default_secondaryCellGroup() is moved to nr_rrc_config.c.
Furthermore, the signature is changes to return the NR_CellGroupConfig
from the functions, instead of filling a pre-allocated structure (which
is, in all cases, allocated just before calling
fill_default_secondaryCellGroup().

There is a problem with this function: the function also fills the
ServingCellConfig (a parameter to this function). This behavior has not
been changed.