ACPI: scan: Relocate acpi_bus_trim_one()

Relocate acpi_bus_trim_one() (without modifications) so as to avoid the
need to add a forward declaration of it in a subsequent patch.

No functional changes.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>