Merge branch 'dsa-mv88e6xxx-refactor-statistics-ready-for-rmu-support'

Andrew Lunn says:

====================
dsa: mv88e6xxx: Refactor statistics ready for RMU support

Marvell Ethernet switches support sending commands to the switch
inside Ethernet frames, which the Remote Management Unit, RMU,
handles. One such command retries all the RMON statistics. The
switches however have other statistics which cannot be retried by this
bulk method, so need to be gathered individually.

This patch series refactors the existing statistics code into a
structure that will allow RMU integration in a future patchset.

There should be no functional change as a result of this refactoring.
====================

Link: https://patch.msgid.link/20241207-v6-13-rc1-net-next-mv88e6xxx-stats-refactor-v1-0-b9960f839846@lunn.ch
Signed-off-by: Jakub Kicinski <kuba@kernel.org>