hw/acpi: Rename and move build_x86_acpi_pci_hotplug to pcihp

hw/acpi: Rename and move build_x86_acpi_pci_hotplug to pcihp

We plan to reuse build_x86_acpi_pci_hotplug() implementation
for ARM so let's move the code to generic pcihp.

Associated static aml_pci_pdsm() helper is also moved along.
build_x86_acpi_pci_hotplug is renamed into build_acpi_pci_hotplug().

No code change intended.

Also fix the reference to acpi_pci_hotplug.rst documentation

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: <20250714080639.2525563-3-eric.auger@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>