ACPI MADT advertises GITS even when disabled
Description of problem:
As per the command line given above, QEMU shall emulate a GICv4 without GIC Interrupt Translation Service (GITS).

The following happens:
- ACPI **incorrectly** lists a GITS (type 0xf) structure in the MADT with GITS MMIO Base = 0x8080000
- The OS reads that structure and interprets it to mean a GITS is present at the given MMIO address
- Subsequent access to GITS MMIO causes a data abort (0x25) because QEMU doesn't emulate a GITS (as requested)

The bug is thus that QEMU wrongly advertises GITS as present (via the MADT) when it is in fact absent.
Steps to reproduce:
1. Disable GITS emulation by passing `its=off` on the QEMU command line
2. Check if a GITS structure is listed in the ACPI MADT (must be present in ACPI MADT only if GITS is enabled and absent otherwise)
Additional information:
When booting with `its=on` (default), everything works as expected.