mlxsw: spectrum: Tolerate enslaving of various devices to VRF

Enslaving netdevices to VRF is currently handled through an
mlxsw_sp_is_vrf_event() conditional in mlxsw_sp_netdevice_event(). In the
following patch sets, VRF enslavement will be handled purely in the router
code. Therefore make handlers of NETDEV_PRECHANGEUPPER tolerant of
enslaving to VRF, so that they do not bounce the change.

For NETDEV_CHANGEUPPER, drop the WARN_ON(1) and bounce from
mlxsw_sp_netdevice_port_vlan_event(). This is the only handler that warned
and bounces even in the CHANGEUPPER code, other handler quietly do nothing
when they encounter an unfamiliar upper.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>