vxlan: Notify for each remote of a removed FDB entry

When notifications are sent about FDB activity, and an FDB entry with
several remotes is removed, the notification is sent only for the first
destination. That makes it impossible to distinguish between the case
where only this first remote is removed, and the one where the FDB entry
is removed as a whole.

Therefore send one notification for each remote of a removed FDB entry.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>