net: dsa: mv88e6xxx: pass mv88e6xxx_chip structure to port_max_speed_mode

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@bootlin.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>