mlxsw: spectrum_flower: Add support for ip ttl

Support offloading rules that match on ip ttl.

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>