PROBLEM: In PNF mode, L1 is started from nfapi_pnf.c without verifying RU
readiness. The only gate is config_sync_var, but nr_softmodem.c sets this before
the RU (e.g., FHI-72) is actually started. As a result, START_REQUEST can
trigger L1 init while the RU is not yet ready -- this is an issue when using
FHI72 with DPDK BBDEV, where a pre-mature L1 init will crash the entire program
as DPDK BBDEV depends on xRAN's DPDK EAL.
FIX: Perform RU readiness checks before setting config_sync_var in NFAPI PNF mode.
This aligns PNF behavior with other modes and prevents L1 from starting before the
RU is operational.