Merge branch 'clean-up-pcs-xpcs-accessors'

Russell King says:

====================
Clean up pcs-xpcs accessors

This series cleans up the pcs-xpcs code to use mdiodev accessors for
read/write just like xpcs_modify_changed() does. In order to do this,
we need to introduce the mdiodev clause 45 accessors.
====================

Link: https://lore.kernel.org/r/Y2pm13+SDg6N/IVx@shell.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>