net: dsa: Remove fixed_link_update member

We have not had a switch driver use a fixed_link_update callback since
58d56fcc ("net: dsa: bcm_sf2: Get rid of
PHYLIB functions") remove this callback.

Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/20240430164816.2400606-2-florian.fainelli@broadcom.com


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