hw/arm/virt: Add a control for the the highmem redistributors

hw/arm/virt: Add a control for the the highmem redistributors

Just like we can control the enablement of the highmem PCIe region
using highmem_ecam, let's add a control for the highmem GICv3
redistributor region.

Similarily to highmem_ecam, these redistributors are disabled when
highmem is off.

Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-id: 20220114140741.1358263-3-maz@kernel.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>