Merge branch 'prepare-ocelot-for-external-interface-control'

Colin Foster says:

====================
prepare ocelot for external interface control

This patch set is derived from an attempt to include external control
for a VSC751[1234] chip via SPI. That patch set has grown large and is
getting unwieldy for reviewers and the developers... me.

I'm breaking out the changes from that patch set. Some are trivial
  net: dsa: ocelot: remove unnecessary pci_bar variables
  net: dsa: ocelot: felix: Remove requirement for PCS in felix devices

some are required for SPI
  net: dsa: ocelot: felix: add interface for custom regmaps

and some are just to expose code to be shared
  net: mscc: ocelot: split register definitions to a separate file

The entirety of this patch set should have essentially no impact on the
system performance.
====================

Link: https://lore.kernel.org/r/20211207170030.1406601-1-colin.foster@in-advantage.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>