PCI: hotplug: Switch to pci_get_bus_and_slot

Thank you so much for your check & advise.
This time, I've tried on ibmphp_core.c, is it OK?

Signed-off-by: Joonwoo Park <joonwpark81@gmail.com>
Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>