PCI: export __pci_reenable_device()

Some odd ACPI implementations choke if certain controller is disabled
when ACPI suspend is invoked but we still need to make sure the PCI
device is enabled during resume.  Simply using pci_enable_device()
unbalances device enable count.  Export __pci_reenable_device().

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>