Merge branch 'net-dsa-qca8k-code-split-for-qca8k'

Christian Marangi says:

====================
net: dsa: qca8k: code split for qca8k

This is needed ad ipq4019 SoC have an internal switch that is
based on qca8k with very minor changes. The general function is equal.

Because of this we split the driver to common and specific code.

As the common function needs to be moved to a different file to be
reused, we had to convert every remaining user of qca8k_read/write/rmw
to regmap variant.
We had also to generilized the special handling for the ethtool_stats
function that makes use of the autocast mib. (ipq4019 will have a
different tagger and use mmio so it could be quicker to use mmio instead
of automib feature)
And we had to convert the regmap read/write to bulk implementation to
drop the special function that makes use of it. This will be compatible
with ipq4019 and at the same time permits normal switch to use the eth
mgmt way to send the entire ATU table read/write in one go.
====================

Link: https://lore.kernel.org/r/20220727113523.19742-1-ansuelsmth@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>