nfp: return -EOPNOTSUPP from .ndo_get_phys_port_name for VFs

After recent change we started returning 0 from
ndo_get_phys_port_name for VFs.  The name parameter for
ndo_get_phys_port_name is not initialized by the stack so
this can lead to a crash.  We should have kept returning
-EOPNOTSUPP in the first place.
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/nfp_net_common.c

@@ -3286,11 +3286,12 @@ nfp_net_get_phys_port_name(struct net_device *netdev, char *name, size_t len)
 	if (nn->port)
 		return nfp_port_get_phys_port_name(netdev, name, len);
 
-	if (!nn->dp.is_vf) {
-		n = snprintf(name, len, "%d", nn->id);
-		if (n >= len)
-			return -EINVAL;
-	}
+	if (nn->dp.is_vf)
+		return -EOPNOTSUPP;
+
+	n = snprintf(name, len, "%d", nn->id);
+	if (n >= len)
+		return -EINVAL;
 
 	return 0;
 }