bridge: switchdev: Let device drivers determine FDB offload indication

Currently, FDB entries that are notified to the bridge via
'SWITCHDEV_FDB_ADD_TO_BRIDGE' are always marked as offloaded. With MAB
enabled, this will no longer be universally true. Device drivers will
report locked FDB entries to the bridge to let it know that the
corresponding hosts required authorization, but it does not mean that
these entries are necessarily programmed in the underlying hardware.

Solve this by determining the offload indication based of the
'offloaded' bit in the FDB notification.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>