mlxsw: spectrum_switchdev: Check notification relevance based on upper device

[ Upstream commit 5050f6ae253ad1307af3486c26fc4f94287078b7 ]

VxLAN FDB updates are sent with the VxLAN device which is not our upper
and will therefore be ignored by current code.

Solve this by checking whether the upper device (bridge) is our upper.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>