PCI: Remove duplicate pci_disable_device() from pcie_portdrv_remove()

The pcie_portdrv .probe() method calls pci_enable_device() once, in
pcie_port_device_register(), but the .remove() method calls
pci_disable_device() twice, in pcie_port_device_remove() and in
pcie_portdrv_remove().

That causes a "disabling already-disabled device" warning when removing a
PCIe port device.  This happens all the time when removing Thunderbolt
devices, but is also easy to reproduce with, e.g.,
"echo 0000:00:1c.3 > /sys/bus/pci/drivers/pcieport/unbind"

This patch removes the disable from pcie_portdrv_remove().

[bhelgaas: changelog, tag for stable]
Reported-by: David Bulkow <David.Bulkow@stratus.com>
Reported-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org	# v2.6.32+