mlxsw: spectrum_dpipe: Fix host table dump

During the neighbor traversal the neighbors from different families
should be ignored.

Fixes: c58035a74aba ("mlxsw: spectrum_dpipe: Add support for IPv4 host table dump")
Signed-off-by: Arkadi Sharshevsky <arkadis@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>