mlxsw: spectrum_switchdev: Don't ignore deletions of learned MACs

Demands to remove FDB entries should be honored even if the FDB entry in
question was originally learned, and not added by the user. Therefore
ignore the added_by_user datum for SWITCHDEV_FDB_DEL_TO_DEVICE.

Fixes: 816a3bed

 ("switchdev: Add fdb.added_by_user to switchdev notifications")
Signed-off-by: Petr Machata <petrm@mellanox.com>
Suggested-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>