net: dsa: microchip: add ksz9563 to ksz9477 I2C driver

Add support for the KSZ9563 3-Port Gigabit Ethernet Switch to the
ksz9477 driver. The KSZ9563 supports both SPI (already in) and I2C. The
ksz9563 is already in the device tree binding documentation.

Signed-off-by: Christian Eggers <ceggers@arri.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>