Look up xran_fh_init/xran_fh_config through driver instead of peaking
into xran internals. Note that xran writes values back into these
structs during initialization, and hence it is important to store them
_after initialization_.
Some remarks regarding less obvious changes:
- slotnum is replaced by slots_in_sf: SLOTNUM_PER_SUBFRAME uses the time
duration of a slot (=interval_us_local) to calculate the numbers of
slots in a subframe, which can be done with a simple shift instead
- The prach duration should be queried from the PRACH configuration
table. The function to query the occasion info is part of the MAC
layer code while this information can be used outside of this layer.
Use header `nr_prach_config.h` to not duplicate functionality.
Co-authored-by: Romain Beurdouche <romain.beurdouche@eurecom.fr>
