hw/arm/virt: Drop superfluous checks against highmem

hw/arm/virt: Drop superfluous checks against highmem

Now that the devices present in the extended memory map are checked
against the available PA space and disabled when they don't fit,
there is no need to keep the same checks against highmem, as
highmem really is a shortcut for the PA space being 32bit.

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Message-id: 20220114140741.1358263-7-maz@kernel.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>