igb: fix a compile warning

control these three function declarations and
definitions with same macro CONFIG_PCI_IOV

drivers/net/ethernet/intel/igb/igb_main.c:165:
warning: ‘igb_vf_configure’ declared ‘static’ but never defined
drivers/net/ethernet/intel/igb/igb_main.c:166:
warning: ‘igb_find_enabled_vfs’ declared ‘static’ but never defined
drivers/net/ethernet/intel/igb/igb_main.c:167:
warning: ‘igb_check_vf_assignment’ declared ‘static’ but never defined

Signed-off-by: RongQing Li <roy.qing.li@gmail.com>
Acked-by: Greg Rose <gregory.v.rose@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/intel/igb/igb_main.c

@@ -162,9 +162,12 @@ static int igb_ndo_set_vf_bw(struct net_device *netdev, int vf, int tx_rate);
 static int igb_ndo_get_vf_config(struct net_device *netdev, int vf,
 				 struct ifla_vf_info *ivi);
 static void igb_check_vf_rate_limit(struct igb_adapter *);
+
+#ifdef CONFIG_PCI_IOV
 static int igb_vf_configure(struct igb_adapter *adapter, int vf);
 static int igb_find_enabled_vfs(struct igb_adapter *adapter);
 static int igb_check_vf_assignment(struct igb_adapter *adapter);
+#endif
 
 #ifdef CONFIG_PM
 static int igb_suspend(struct pci_dev *, pm_message_t);