kni: fix ethtool build with kernel 4.11

build error:
.../lib/librte_eal/linuxapp/kni/igb_main.c:1034:10:
error: implicit declaration of function ‘pci_enable_msix’
    err = pci_enable_msix(pdev,
              ^~~~~~~~~~~~~~~

This build error observed when CONFIG_RTE_KNI_KMOD_ETHTOOL config option
enabled.

Following Linux commit removes the pci_enable_msix()
Linux: 4244de1c64de ("PCI: remove pci_enable_msix")

Switch to pci_enable_msix_range() for kernel > 4.8 since current Linux
igb driver uses this function.

Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>

lib/librte_eal/linuxapp/kni/ethtool/igb/igb_main.c

@@ -1031,8 +1031,15 @@ static void igb_set_interrupt_capability(struct igb_adapter *adapter, bool msix)
 			for (i = 0; i < numvecs; i++)
 				adapter->msix_entries[i].entry = i;
 
+#ifdef HAVE_PCI_ENABLE_MSIX
 			err = pci_enable_msix(pdev,
 			                      adapter->msix_entries, numvecs);
+#else
+			err = pci_enable_msix_range(pdev,
+					adapter->msix_entries,
+					numvecs,
+					numvecs);
+#endif
 			if (err == 0)
 				break;
 		}

lib/librte_eal/linuxapp/kni/ethtool/igb/kcompat.h

@@ -3937,4 +3937,8 @@ skb_set_hash(struct sk_buff *skb, __u32 hash, __always_unused int type)
 #define HAVE_VF_VLAN_PROTO
 #endif /* >= 4.9.0, >= SLES12SP3 */
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 8, 0)
+#define HAVE_PCI_ENABLE_MSIX
+#endif
+
 #endif /* _KCOMPAT_H_ */