mlxsw: spectrum_router: Do not force specific configuration order

In symmetric routing, the only two members in the VLAN corresponding to
the L3 VNI are the router port and the VXLAN tunnel.

In case the VXLAN device is already enslaved to the bridge and only
later the VLAN interface is configured, the tunnel will not be
offloaded.

The reason for this is that when the router interface (RIF)
corresponding to the VLAN interface is configured, it calls the core
fid_get() API which does not check if NVE should be enabled on the FID.

Instead, call into the bridge code which will check if NVE should be
enabled on the FID.

This effectively means that the same code path is used to retrieve a FID
when either a local port or a router port joins the FID.

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