BCM5325 doesn't implement GMII_PORT_OVERRIDE_CTRL register so we should
avoid reading or writing it.
PORT_OVERRIDE_RX_FLOW and PORT_OVERRIDE_TX_FLOW aren't defined on BCM5325
and we should use PORT_OVERRIDE_LP_FLOW_25 instead.
Fixes: 5e004460f874 ("net: dsa: b53: Add helper to set link parameters")
Signed-off-by: Álvaro Fernández Rojas <noltari@xxxxxxxxx>