mlxsw: spectrum: Support IPIP overlay VRF migration

IPIP entries are created as soon as an offloadable device is created.
That means that when such a device is later moved to a different VRF,
the loopback device that backs the tunnel is wrong.

Thus when an offloadable encapsulating netdevice moves from one VRF to
another, make sure that the loopback is updated as necessary.

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