net: dsa: microchip: add separate struct ksz_chip_data for KSZ8563 chip

Add separate entry for the KSZ8563 chip. According to the documentation
it can support Gbit only on RGMII port. So, we will need to be able to
describe in the followup patch.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>