tests/acpi/bios-tables-test: add and allow changes to a new q35 DSDT table blob

tests/acpi/bios-tables-test: add and allow changes to a new q35 DSDT table blob

We are adding a new unit test to cover the acpi hotplug support in q35 for
multi-function bridges. This test uses a new table DSDT.multi-bridge.
We need to allow changes in DSDT acpi table for addition of this new
unit test.

Signed-off-by: Ani Sinha <ani@anisinha.ca>
Message-Id: <20211007135750.1277213-2-ani@anisinha.ca>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Igor Mammedov <imammedo@redhat.com>