hw/i386/acpi-build: Move build_append_pci_bus_devices/pcihp_slots to pcihp

hw/i386/acpi-build: Move build_append_pci_bus_devices/pcihp_slots to pcihp

We intend to reuse build_append_pci_bus_devices and build_append_pcihp_slots
on ARM. So let's move them to hw/acpi/pcihp.c as well as all static
helpers they use.

No functional change intended.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Gustavo Romero <gustavo.romero@linaro.org>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Message-Id: <20250714080639.2525563-15-eric.auger@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>