net: mscc: ocelot: offload per-flow mirroring using tc-mirred and VCAP IS2

Per-flow mirroring with the VCAP IS2 TCAM (in itself handled as an
offload for tc-flower) is done by setting the MIRROR_ENA bit from the
action vector of the filter. The packet is mirrored to the port mask
configured in the ANA:ANA:MIRRORPORTS register (the same port mask as
the destinations for port-based mirroring).

Functionality was tested with:

tc qdisc add dev swp3 clsact
tc filter add dev swp3 ingress protocol ip \
	flower skip_sw ip_proto icmp \
	action mirred egress mirror dev swp1

and pinging through swp3, while seeing that the ICMP replies are
mirrored towards swp1.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>