net: dsa: mv88e6352: Add support for ndo_fdb functions

Add support for manipulating switch fdb entries by pointing to the
ndo_fdb functions implemented for mv88e6xxxx.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: David S. Miller <davem@davemloft.net>