net: Define NETDEV_FCOE_WWNN, NETDEV_FCOE_WWPN only when CONFIG_LIBFCOE is enabled

bnx2fc driver calls netdev->netdev_ops->ndo_fcoe_get_wwn() and it may not
be defined with the current Kconfig dependencies.  ndo_fcoe_get_wwn is
dependent on CONFIG_FCOE, but bnx2fc does not select CONFIG_FCOE, as it does
not depend on fcoe driver. Since both fcoe and bnx2fc drivers select
CONFIG_LIBFCOE, define NETDEV_FCOE_WWNN and NETDEV_FCOE_WWPN when
CONFIG_LIBFCOE is defined.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: Randy Dunlap <rdunlap@xenotime.net>
Cc: Yi Zou <yi.zou@intel.com>
Signed-off-by: Bhanu Prakash Gollapudi <bprakash@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Reviewed-by: Yi Zou <yi.zou@intel.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -922,11 +922,15 @@ struct net_device_ops {
 						       u16 xid,
 						       struct scatterlist *sgl,
 						       unsigned int sgc);
+#endif
+
+#if defined(CONFIG_LIBFCOE) || defined(CONFIG_LIBFCOE_MODULE)
 #define NETDEV_FCOE_WWNN 0
 #define NETDEV_FCOE_WWPN 1
 	int			(*ndo_fcoe_get_wwn)(struct net_device *dev,
 						    u64 *wwn, int type);
 #endif
+
 #ifdef CONFIG_RFS_ACCEL
 	int			(*ndo_rx_flow_steer)(struct net_device *dev,
 						     const struct sk_buff *skb,