ixgb: call pci_disable_device in ixgb_remove

ixgb fails to work after reload on recent kernels:

rmmod ixgb (dev->current_state = PCI_UNKNOWN)
modprobe ixgb (pci_enable_device will bail leaving current_state to PCI_UNKNOWN)
ifup eth0
do_IRQ: 2.82 No irq handler for vector (irq -1)

The issue was exposed by commit fcd097f3
PCI: MSI: Remove unsafe and unnecessary hardware access

which avoids HW writes for power states != PCI_D0

CC: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: NEmil Tantilov <emil.s.tantilov@intel.com>
Tested-by: NJeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ixgb/ixgb_main.c

@@ -533,6 +533,7 @@ ixgb_remove(struct pci_dev *pdev)
 	pci_release_regions(pdev);
 
 	free_netdev(netdev);
+	pci_disable_device(pdev);
 }
 
 /**