lldp: set correct state for processing

ldp_receive_frame after correct processing of the packet the state
should be LLDP_AGENT_RX_WAIT_FOR_FRAME not LLDP_AGENT_RX_UPDATE_INFO.

src/libsystemd-network/sd-lldp.c

@@ -133,8 +133,6 @@ static int lldp_receive_frame(sd_lldp *lldp, tlv_packet *tlv) {
 
         lldp->statistics.stats_frames_in_total ++;
 
-        return 0;
-
  out:
         if (r < 0)
                 log_lldp("Receive frame failed: %s", strerror(-r));