From: Alexis Lothoré <alexis.lothore@xxxxxxxxxxx>
Some switches families have minor differences on supported link speed for
ports. Instead of redefining a new port_max_speed_mode for each different
configuration, allow to pass mv88e6xxx_chip structure to allow
differentiating those chips by known chip id
Signed-off-by: Alexis Lothoré <alexis.lothore@xxxxxxxxxxx>