ixgb: call pci_disable_device in ixgb_remove

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 84b046c60e40c5810b114339b819aabb12405707
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: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>