ACPI / hotplug / PCI: Drop acpiphp_bus_trim()

If trim_stale_devices() calls acpi_bus_trim() directly, we can
save a potentially costly acpi_bus_get_device() invocation.  After
making that change acpiphp_bus_trim() would only be called from one
place, so move the code from it to that place and drop it.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>