The KSZ9477 SPI driver already has support for the KSZ8563. The same switch
chip can also be managed via i2c and we have an KSZ9477 I2C driver, but
that one lacks the relevant compatible entry. Add it.

DT bindings already describe this compatible.
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>