net/mlx4_en: Implement ndo fdb functionality

Add support for setting embedded switch fdb in case of SRIOV, by
implementing ndo_fdb_{add, del, dump}. This will allow to use
bridged configuration with multi-function. In order to add VM MAC
to the eSwitch fdb, the following command may be used over the relevant function interface:
bridge fdb add <MAC> permanent self dev <IFACE>

Signed-off-by: Yan Burman <yanb@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>