mlx4: Remove driver specific fdb handlers.

Remove driver specific fdb hadlers since they are the same as
the default ones.

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