net/mlx5e: Fix pfnum in devlink port attribute

Cited patch missed to extract PCI pf number accurately for PF and VF
port flavour. It considered PCI device + function number.
Due to this, device having non zero device number shown large pfnum.

Hence, use only PCI function number; to avoid similar errors, derive
pfnum one time for all port flavours.

Fixes: f60f315d

 ("net/mlx5e: Register devlink ports for physical link, PCI PF, VFs")
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>