Since commit 71b77a7a27a3 ("enetc: Migrate to PHYLINK and PCS_LYNX") the
network port of the Kontron sl28 board is broken. After the migration to
phylink the device tree has to specify the in-band-mode property. Add
it.
Fixes: 71b77a7a27a3 ("enetc: Migrate to PHYLINK and PCS_LYNX")
Suggested-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
Signed-off-by: Michael Walle <michael@xxxxxxxx>