silenced a few warnings

eigrp_packet.c:911:50: warning: variable 'length' is uninitialized when
used here [-Wuninitialized]
      eigrp_hello (eigrp, iph, eigrph, ibuf, ei, length);

eigrp_packet.c:1271:29: warning: unused variable 'ep_multicast'
[-Wunused-variable]
  struct eigrp_packet *ep, *ep_multicast;