nfp: initialize netdev's dev_port with correct id

nfp: initialize netdev's dev_port with correct id

`dev_port` is used to differentiate devices that instantiate from
the same function, which is the case in most of NFP NICs.

In some customized scenario, `dev_port` is used to rename netdev
instead of `phys_port_name`. Example rules using `dev_port`:

  SUBSYSTEM=="net", ACTION=="add", KERNELS=="0000:e1:00.0", ATTR{dev_port}=="0", NAME:="ens8np0"
  SUBSYSTEM=="net", ACTION=="add", KERNELS=="0000:e1:00.0", ATTR{dev_port}=="1", NAME:="ens8np1"

To take port split case into account, here we initialize `dev_port`
according to the port sequence in eth_table from management firmware
instead of using port label id directly. And management firmware
makes sure that port sequence matches its label id.

Signed-off-by: Yinjun Zhang <yinjun.zhang@corigine.com>
Acked-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Louis Peens <louis.peens@corigine.com>
Link: https://lore.kernel.org/r/20230405120829.28817-1-louis.peens@corigine.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>