mlxsw: spectrum_router: Don't abort on l3mdev rules

mlxsw: spectrum_router: Don't abort on l3mdev rules

Now that port netdevs can be enslaved to a VRF master we need to make
sure the device's routing tables won't be flushed upon the insertion of
a l3mdev rule.

Note that we assume the notified l3mdev rule is a simple rule as used by
the VRF master. We don't check for the presence of other selectors such
as 'iif' and 'oif'.

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>