vxlan: Avoid unnecessary updates to FDB 'used' time

Now that the VXLAN driver ages out FDB entries based on their 'updated'
time we can remove unnecessary updates of the 'used' time from the Rx
path and the control path, so that the 'used' time is only updated by
the Tx path.

Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20250204145549.1216254-8-idosch@nvidia.com


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