Merge branch 'enetc-Migrate-to-PHYLINK-and-PCS_LYNX'

Claudiu Manoil says:

====================
enetc: Migrate to PHYLINK and PCS_LYNX

Transitioning the enetc driver from phylib to phylink.
Offloading the serdes configuration to the PCS_LYNX
module is a mandatory part of this transition. Aiming
for a cleaner, more maintainable design, and better
code reuse.
The first 2 patches are clean up prerequisites.

Tested on a p1028rdb board.

v2: validate() explicitly rejects now all interface modes not
supported by the driver instead of relying on the device tree
to provide only supported interfaces, and dropped redundant
activation of pcs_poll (addressing Ioana's findings)
====================

Signed-off-by: Jakub Kicinski <kuba@kernel.org>