net/mlx5e: Support routed networks during IPsec MACs initialization

net/mlx5e: Support routed networks during IPsec MACs initialization

Remote IPsec tunnel endpoint may refer to a network segment that is
not directly connected to the host. In such a case, IPsec tunnel
endpoints are connected to a router and reachable via a routing path.
In IPsec packet offload mode, HW is initialized with the MAC address
of both IPsec tunnel endpoints.

Extend the current IPsec init MACs procedure to resolve nexthop for
routed networks. Direct neighbour lookup and probe is still used
for directly connected networks and as a fallback mechanism if fib
lookup fails.

Signed-off-by: Alexandre Cassen <acassen@corp.free.fr>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Link: https://patch.msgid.link/1753194228-333722-2-git-send-email-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>