Fix FAPI WLS slot.indication slot ahead

Current FAPI slot_ahead value for WLS is too low for UL, as we see these
errors:

    [NR_MAC] Unexpected ULSCH HARQ PID 14 (have 3) for RNTI 0xa68e
    [NR_MAC] UE a68e expected HARQ pid 3 feedback at  586. 7, but is at  587.17 instead (HARQ feedback is in the past)

Similarly to nFAPI, scale it by mu (for mu=1 => slot_ahead=2) to give
additional time, which removes these warnings at the VNF.

nfapi/oai_integration/nfapi_pnf.c

@@ -2315,7 +2315,7 @@ void handle_nr_slot_ind(uint16_t sfn, uint16_t slot, NR_Sched_Rsp_t *sched_resp)
 #ifndef ENABLE_WLS
   int slot_ahead = 2 << mu;
 #else
-  int slot_ahead = 1;
+  int slot_ahead = 1 << mu;
 #endif
   uint16_t sfn_tx = sfn;
   uint16_t slot_tx = slot;