fix typo in nr_slot_fep_init_sync()

This function is used during initial synchronization, only.
This typo leads to wrong computation of the OFDM symbol start within a slot, after PBCH decoding.
The result is a time offset and therefore a rotation in frequency domain for the initial PDCCH and PDSCH (SIB1) reception.

openair1/PHY/MODULATION/slot_fep_nr.c

@@ -148,7 +148,7 @@ int nr_slot_fep_init_sync(PHY_VARS_NR_UE *ue,
   unsigned int rx_offset   = sample_offset + slot_offset;
   unsigned int abs_symbol  = Ns * frame_parms->symbols_per_slot + symbol;
   for (int idx_symb = Ns*frame_parms->symbols_per_slot; idx_symb <= abs_symbol; idx_symb++)
-    rx_offset += (abs_symbol%(0x7<<frame_parms->numerology_index)) ? nb_prefix_samples : nb_prefix_samples0;
+    rx_offset += (idx_symb%(0x7<<frame_parms->numerology_index)) ? nb_prefix_samples : nb_prefix_samples0;
   rx_offset += frame_parms->ofdm_symbol_size * symbol;
 
 #ifdef DEBUG_FEP