net: mscc: ocelot: use ipv6 in the aggregation code

IPv6 header information is not currently part of the entropy source for
the 4-bit aggregation code used for LAG offload, even though it could be.
The hardware reference manual says about these fields:

ANA::AGGR_CFG.AC_IP6_TCPUDP_PORT_ENA
Use IPv6 TCP/UDP port when calculating aggregation code. Configure
identically for all ports. Recommended value is 1.

ANA::AGGR_CFG.AC_IP6_FLOW_LBL_ENA
Use IPv6 flow label when calculating AC. Configure identically for all
ports. Recommended value is 1.

Integration with the xmit_hash_policy of the bonding interface is TBD.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>