net: dsa: LAN9303: Add basic support for LAN9354

Adding support for the LAN9354 device by allowing it to use
the LAN9303 DSA driver.  These devices have the same underlying
access and control methods and from a feature set point of view
the LAN9354 is a superset of the LAN9303.

The MDIO access method has been tested on a SAMA5D3-EDS board
with a LAN9354 RMII daughter card.

While the SPI access method should also be the same, it has not
been tested and as such is not included at this time.

Signed-off-by: Jerry Ray <jerry.ray@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>