bios-tables-test: allow changes in DSDT ACPI tables for q35

We are going to commit a change to fix IO address range allocated for acpi pci
hotplug in q35. This affects DSDT tables. This change allows DSDT table
modification so that unit tests are not broken.

Signed-off-by: Ani Sinha <ani@anisinha.ca>
Acked-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20210916132838.3469580-2-ani@anisinha.ca>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>