mlxsw: spectrum: Mark packets trapped in router

In commit 1c6c6d22 ("mlxsw: spectrum: Mirror certain packets to
CPU") we marked packets that were mirrored to the CPU, so that they
won't be flooded again by the bridge driver.

However, certain packets are trapped in the device's router block, after
passing through the bridge block where they were potentially flooded.

Mark all packets coming from L3 traps, so that they won't be potentially
flooded again by the bridge driver.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>