ndo_fdb_add: Add a parameter to report whether notification was sent

Currently when FDB entries are added to or deleted from a VXLAN netdevice,
the VXLAN driver emits one notification, including the VXLAN-specific
attributes. The core however always sends a notification as well, a generic
one. Thus two notifications are unnecessarily sent for these operations. A
similar situation comes up with bridge driver, which also emits
notifications on its own:

 # ip link add name vx type vxlan id 1000 dstport 4789
 # bridge monitor fdb &
 [1] 1981693
 # bridge fdb add de:ad:be:ef:13:37 dev vx self dst 192.0.2.1
 de:ad:be:ef:13:37 dev vx dst 192.0.2.1 self permanent
 de:ad:be:ef:13:37 dev vx self permanent

In order to prevent this duplicity, add a paremeter to ndo_fdb_add,
bool *notified. The flag is primed to false, and if the callee sends a
notification on its own, it sets it to true, thus informing the core that
it should not generate another notification.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/cbf6ae8195e85cbf922f8058ce4eba770f3b71ed.1731589511.git.petrm@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>