neigh: Use neigh table index for neigh_packet_xmit

Remove a little bit of unnecessary work when transmitting a packet with
neigh_packet_xmit.  Use the neighbour table index not the address family
as a parameter.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc include/net/neighbour.h
Simple merge

diff --cc net/core/neighbour.c
Simple merge

diff --cc net/mpls/af_mpls.c
Simple merge