mlxsw: spectrum_dpipe: Add IPv6 host table initial support

Add IPv6 host table initial support. The action behavior for both IPv4/6
tables is the same, thus the same action dump op is used. Neighbors with
link local address are ignored.

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>