net: phylink: remove .validate() method

The MAC .validate() method is no longer used, so remove it from the
phylink_mac_ops structure, and remove the callsite in
phylink_validate_mac_and_pcs().

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/E1qsPkF-009wij-QM@rmk-PC.armlinux.org.uk


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