Merge branch 'net-dsa-mv88e6xxx-accelerate-c45-scan'

Klaus Kudielka says:

====================
net: dsa: mv88e6xxx: accelerate C45 scan

Starting with commit 1a136ca ("net: mdio: scan bus based on bus
capabilities for C22 and C45"), mdiobus_scan_bus_c45() is being called on
buses with MDIOBUS_NO_CAP. On a Turris Omnia (Armada 385, 88E6176 switch),
this causes a significant increase of boot time, from 1.6 seconds, to 6.3
seconds. The boot time stated here is until start of /init.

Further testing revealed that the C45 scan is indeed expensive (around
2.7 seconds, due to a huge number of bus transactions), and called twice.

Two things were suggested:
(1) to move the expensive call of mv88e6xxx_mdios_register() from
    mv88e6xxx_probe() to mv88e6xxx_setup().
(2) to mask apparently non-existing phys during probing.

Before that:
Patch #1 prepares the driver to handle the movement of
mv88e6xxx_mdios_register() to mv88e6xxx_setup() for cross-chip DSA trees.
Patch #2 is preparatory code movement, without functional change.

With those changes, boot time on the Turris Omnia is back to normal.

Link: https://lore.kernel.org/lkml/449bde236c08d5ab5e54abd73b645d8b29955894.camel@gmail.com/
====================

Link: https://lore.kernel.org/r/20230315163846.3114-1-klaus.kudielka@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>