PCI: hotplug: Remove "Returns" kerneldoc from void functions

pci_hp_deregister() was converted to void by the commit 51bbf9be ("PCI:
hotplug: Demidlayer registration with the core") but its kerneldoc still
describes the return value. pci_hp_del() and pci_hp_destroy() have been
void since they were introduced in that same commit.

Remove the return value description from the kerneldoc of those functions.

Link: https://lore.kernel.org/r/20240930124436.17908-1-ilpo.jarvinen@linux.intel.com


Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>