mlxsw: spectrum: Create PVID vPort before registering netdevice

After registering a netdevice it's possible for user space applications
to configure an IP address on it. From the driver's perspective, this
means a router interface (RIF) should be created for the PVID vPort.

Therefore, we must create the PVID vPort before registering the
netdevice.

Fixes: 99724c18

 ("mlxsw: spectrum: Introduce support for router interfaces")
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>