hw/arm/virt-acpi-build: Fix ACPI IORT and MADT tables when its=off

hw/arm/virt-acpi-build: Fix ACPI IORT and MADT tables when its=off

Currently, the ITS Group nodes in the IORT table and the GIC ITS Struct
in the MADT table are always generated, even if GIC ITS is not available
on the machine.

This commit fixes it by not generating the ITS Group nodes, not mapping
any other node to them, and not advertising the GIC ITS in the MADT
table, when GIC ITS is not available on the machine.

Since the fix changes the MADT and IORT tables, add the blobs for the
"its=off" test to the allow list and update them in the next commit.

This commit also renames the smmu_idmaps and its_idmaps variables in
build_iort() to rc_smmu_idmaps and rc_its_idmaps, respectively, to make
it clearer which nodes are involved in the mappings associated with
these variables.

Reported-by: Udo Steinberg <udo@hypervisor.org>
Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
Message-id: 20250628195722.977078-9-gustavo.romero@linaro.org
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2886
Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
Co-authored-by: Philippe Mathieu-Daudé <philmd@linaro.org>
[PMM: wrapped an overlong comment]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>