acpi: pci: move BSEL into build_append_pcihp_slots()

acpi: pci: move BSEL into build_append_pcihp_slots()

Generic PCI enumeration code doesn't really need access to
BSEL value, it is only used as means to decide if hotplug
enumerator should be called.

Use stateless object_property_find() to do that, and move
the rest of BSEL handling into build_append_pcihp_slots()
where it belongs.

This cleans up generic code a bit from hotplug stuff
and follow up patch will remove remaining call to
build_append_pcihp_slots() from generic code, making
it possible to use without ACPI PCI hotplug dependencies.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20230302161543.286002-32-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>