PCI Hotplug: convert acpi_pci_detect_ejectable() to take an acpi_handle

acpi_pci_detect_ejectable() goes through effort to convert its
struct pci_bus arg to an acpi_handle, but every time we use this
interface, we already have the handle available.

So let's just use the handle instead of converting back and forth.

Reviewed-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Tested-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>