Convert pci_delete_child() to a bus_child_deleted() method.

Instead of providing a wrapper around device_delete_child() that the PCI
bus and child bus drivers must call explicitly, move the bulk of the logic
from pci_delete_child() into a bus_child_deleted() method
(pci_child_deleted()). This allows PCI devices to be safely deleted via
device_delete_child().

• Add a bus_child_deleted method to the ACPI PCI bus which clears the device_t associated with the corresponding ACPI handle in addition to the normal PCI bus cleanup.
• Change cardbus_detach_card to call device_delete_children() and move CardBus-specific delete logic into a new cardbus_child_deleted() method.
• Use device_delete_child() instead of pci_delete_child() in the SRIOV code.
• Add a bus_child_deleted method to the OpenFirmware PCI bus drivers which frees the OpenFirmware device info for each PCI device.

To preserve KBI, a pci_delete_child() function is left in place that
just calls device_delete_child().

PR: 226562
Requested by: dexuan