net: dsa: microchip: add ksz9567 to ksz9477 driver

Add support for the KSZ9567 7-Port Gigabit Ethernet Switch to the
ksz9477 driver. The KSZ9567 supports both SPI and I2C. Oddly the
ksz9567 is already in the device tree binding documentation.

Signed-off-by: George McCollister <george.mccollister@gmail.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>