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 fcd097f31a6ee207cc0c3da9cccd2a86d4334785
PCI: MSI: Remove unsafe and unnecessary hardware access

which avoids HW writes for power states != PCI_D0

CC: Ben Hutchings <[e-mail]>
Signed-off-by: Emil Tantilov <[e-mail]>
Tested-by: Jeff Pieper <[e-mail]>
Signed-off-by: Jeff Kirsher <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ixgb/ixgb_main.c

···
 	pci_release_regions(pdev);
 
 	free_netdev(netdev);
+	pci_disable_device(pdev);
 }
 
 /**