PCI: Convert "new_id"/"remove_id" into generic pci_bus driver attributes

This patch removes hardcoded sysfs attributes manipulation and
converts them into generic pci_bus->drv_attrs. This saves several bytes.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>