net: dsa: Add KSZ8567 switch support

This commit introduces support for the KSZ8567, a robust 7-port
Ethernet switch. The KSZ8567 features two RGMII/MII/RMII interfaces,
each capable of gigabit speeds, complemented by five 10/100 Mbps
MAC/PHYs.

Signed-off-by: Philippe Schenker <philippe.schenker@impulsing.ch>
Acked-by: Arun Ramadoss <arun.ramadoss@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/20240130083419.135763-2-dev@pschenker.ch
Signed-off-by: Paolo Abeni <pabeni@redhat.com>