ACPI: Reduce the usage of struct acpi_bus_ops

Objects of type struct acpi_bus_ops are currently used to pass
information between different parts of the ACPI namespace scanning
code, sometimes in quite convoluted ways.  It turns out that that
is not necessary in some cases, so simplify the code by reducing
the utilization of struct acpi_bus_ops objects where clearly
possible.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>
Acked-by: Toshi Kani <toshi.kani@hp.com>