hw/i386/acpi-build: Turn build_q35_osc_method into a generic method

hw/i386/acpi-build: Turn build_q35_osc_method into a generic method

GPEX acpi_dsdt_add_pci_osc() does basically the same as
build_q35_osc_method().

Rename build_q35_osc_method() into build_pci_host_bridge_osc_method()
and move it into hw/acpi/pci.c. In a subsequent patch we will
use this later in place of acpi_dsdt_add_pci_osc().

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20250714080639.2525563-9-eric.auger@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>