Merge branch 'fixes-for-q-usgmii-speeds-and-autoneg'

Maxime Chevallier says:

====================
fixes for Q-USGMII speeds and autoneg

This is the second version of a small changeset for QUSGMII support,
fixing inconsistencies in reported max speed and control word parsing.

As reported here [1], there are some inconsistencies for the Q-USGMII
mode speeds and configuration. The first patch in this fixup series
makes so that we correctly report the max speed of 1Gbps for this mode.

The second patch uses a dedicated helper to decode the control word.
This is necessary as although USGMII control words are close to USXGMII,
they don't support the same speeds.

[1] : https://lore.kernel.org/netdev/ZHnd+6FUO77XFJvQ@shell.armlinux.org.uk/
====================

Link: https://lore.kernel.org/r/20230609080305.546028-1-maxime.chevallier@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>