Merge branch 'net-dsa-mxl862xx-add-support-for-bridge-offloading'

Daniel Golle says:

====================
net: dsa: mxl862xx: add support for bridge offloading

As a next step to complete the mxl862xx DSA driver, add support for
offloading forwarding between bridged ports to the switch hardware.

This works pretty much without any big surprises, apart from two
subtleties:
 * per-port control over flooding behavior has to be implemented by
   (ab)using a 0-rate QoS meters as stopper in lack of any better
   option.
 * STP state transition unconditionally enables learning on a port
   even if it was previously explicitely disabled (a firmware bug)

Note that as the driver is still lacking all VLAN features (which
are going to be added next), at this point some of the
bridge_vlan_aware.sh tests are failing after applying this series.

This is expected and cannot be avoided without implementing
port_vlan_filtering + port_vlan_add/del. And adding both bridge and
VLAN offloading at the same time would be too much for anyone to
review, so VLAN support is going to be submitted in a follow-up
series immediately after this series has been accepted.

All other relevant selftests (including bridge_vlan_unaware.sh) are
still passing.

Inspired by the comments received from Paolo Abeni as reply to v5
the driver now no longer caches bridge port membership in the
driver, but instead imports an existing helper from yt921x.c to dsa.h
in order to allow the driver to easily iterate over bridge members.
The mapping between DSA bridge num and firmware bridge ID is done
using a simple fixed-size array in mxl862xx_priv.
====================

Link: https://patch.msgid.link/cover.1775049897.git.daniel@makrotopia.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>