MIPS: mscc: Add switch to ocelot

Ocelot has an integrated switch, add support for it.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: linux-mips@linux-mips.org
Cc: netdev@vger.kernel.org
Signed-off-by: James Hogan <jhogan@kernel.org>