rename packet_get_layers_number to packet_get_layer_count

src/packet/packet_utils.cpp

@@ -23,7 +23,7 @@ enum packet_origin packet_get_origin(const struct packet *pkt)
     return pkt->origin;
 }
 
-int8_t packet_get_layers_number(const struct packet *pkt)
+int8_t packet_get_layer_count(const struct packet *pkt)
 {
     return pkt->layers_used;
 }