net: dsa: Move FDB dump implementation inside DSA

>From all switchdev devices only DSA requires special FDB dump. This is due
to lack of ability for syncing the hardware learned FDBs with the bridge.
Due to this it is removed from switchdev and moved inside DSA.

Signed-off-by: Arkadi Sharshevsky <arkadis@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>