fixing snprintf issue where return value was used for length calculation

srsue/src/stack/rrc/rrc.cc

@@ -572,12 +572,13 @@ void rrc::sort_neighbour_cells()
                   neighbour_cells[0]->phy_cell.cell.id,
                   neighbour_cells[0]->get_rsrp());
     for (uint32_t i = 1; i < neighbour_cells.size(); i++) {
-      n += snprintf(&ordered[n],
+      int m = snprintf(&ordered[n],
                        512 - n,
                        " | earfcn=%d, pci=%d, rsrp=%.2f",
                        neighbour_cells[i]->get_earfcn(),
                        neighbour_cells[i]->get_pci(),
                        neighbour_cells[i]->get_rsrp());
+      n += m;
     }
     rrc_log->info("Neighbours: %s]\n", ordered);
   } else {