Merge branch 'pci/hotplug'

Merge branch 'pci/hotplug'

- Remove unused cpcihp struct cpci_hp_controller_ops.hardware_test
  (Guilherme Giacomo Simoes)

- Remove unused cpqphp struct ctrl_dbg.ctrl (Christophe JAILLET)

- Clean up cpqphp PCIBIOS_* return value confusion (Ilpo Järvinen)

- Use pci_bus_read_dev_vendor_id() instead of hand-coded presence detection
  in cpqphp (Ilpo Järvinen)

- Simplify cpqphp enumeration, which is already simple-minded and doesn't
  handle devices below hot-added bridges (Ilpo Järvinen)

- Retain a reference to the pci_bus for the lifetime of a pci_slot to avoid
  a use-after-free when the thunderbolt driver resets USB4 host routers on
  boot, causing hotplug remove/add of downstream docks or other devices
  (Lukas Wunner)

* pci/hotplug:
  PCI: Fix use-after-free of slot->bus on hot remove
  PCI: cpqphp: Simplify PCI_ScanBusForNonBridge()
  PCI: cpqphp: Use define to read class/revision dword
  PCI: cpqphp: Use pci_bus_read_dev_vendor_id() to detect presence
  PCI: cpqphp: Fix PCIBIOS_* return value confusion
  PCI: cpqphp: Remove unused struct ctrl_dbg.ctrl
  PCI: cpcihp: Remove unused struct cpci_hp_controller_ops.hardware_test