net: dsa: lantiq_gswip: provide own phylink MAC operations

Convert lantiq_gswip to provide its own phylink MAC operations, thus
avoiding the shim layer in DSA's port.c. For lantiq_gswip, it means
we end up with a common instance of phylink MAC operations that are
shared between the different variants, rather than having duplicated
initialisers in dsa_switch_ops.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/E1rvIcj-006bQo-B3@rmk-PC.armlinux.org.uk


Signed-off-by: Paolo Abeni <pabeni@redhat.com>