Merge branch 'dsa-changes-for-multiple-cpu-ports-part-3'

Vladimir Oltean says:

====================
DSA changes for multiple CPU ports (part 3)

Those who have been following part 1:
https://patchwork.kernel.org/project/netdevbpf/cover/20220511095020.562461-1-vladimir.oltean@nxp.com/
and part 2:
https://patchwork.kernel.org/project/netdevbpf/cover/20220521213743.2735445-1-vladimir.oltean@nxp.com/
will know that I am trying to enable the second internal port pair from
the NXP LS1028A Felix switch for DSA-tagged traffic via "ocelot-8021q".
This series represents part 3 of that effort.

Covered here are some preparations in DSA for handling multiple DSA
masters:
- when changing the tagging protocol via sysfs
- when the masters go down
as well as preparation for monitoring the upper devices of a DSA master
(to support DSA masters under a LAG).

There are also 2 small preparations for the ocelot driver, for the case
where multiple tag_8021q CPU ports are used in a LAG. Both those changes
have to do with PGID forwarding domains.

Compared to v1, the patches were trimmed down to just another
preparation stage, and the UAPI changes were pushed further out to part 4.
https://patchwork.kernel.org/project/netdevbpf/cover/20220523104256.3556016-1-olteanv@gmail.com/

Compared to v2, I had to export a symbol I forgot to
(ocelot_port_teardown_dsa_8021q_cpu), to avoid a build breakage when the
felix and seville drivers are built as modules.
====================

Link: https://lore.kernel.org/r/20220819174820.3585002-1-vladimir.oltean@nxp.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>