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 <[e-mail]>
Reported-by: Randy Dunlap <[e-mail]>
Cc: Yi Zou <[e-mail]>
Signed-off-by: Bhanu Prakash Gollapudi <[e-mail]>
Signed-off-by: Michael Chan <[e-mail]>
Reviewed-by: Yi Zou <[e-mail]>
Acked-by: Randy Dunlap <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/linux/netdevice.h

···
 						       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,