PCI: hotplug: Drop superfluous NULL pointer checks in has_*_file()

PCI: hotplug: Drop superfluous NULL pointer checks in has_*_file()

The PCI hotplug core contains five has_*_file() functions to determine
whether a certain sysfs file shall be added (or removed) for a given
hotplug slot.

The functions perform NULL pointer checks for the hotplug_slot and its
hotplug_slot_ops.  However the callers already perform these checks:

  pci_hp_register()
    __pci_hp_register()
      __pci_hp_initialize()

  pci_hp_deregister()
    pci_hp_del()

The only way to actually trigger these checks is to call pci_hp_add()
without having called pci_hp_initialize().

Amend pci_hp_add() to catch that and drop the now superfluous NULL
pointer checks in has_*_file().

Drop the same superfluous checks from pci_hp_create_module_link(),
which is (only) called from pci_hp_add().

Link: https://lore.kernel.org/r/37d1928edf8c3201a8b10794f1db3142e16e02b9.1740501868.git.lukas@wunner.de
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>