We cache the PCI_EXP_SLTCAP_HPC bit in pci_dev->is_hotplug_bridge on device
probe, so there's no need to read it again on allocation of port service
devices.

No functional change intended.
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>