hw/arm/virt: Remove VirtMachineClass::no_its field The VirtMachineClass::no_its field was only used by virt-2.7 machine, which got removed. Remove it and simplify virt_instance_init() and virt_acpi_build(). Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org> Reviewed-by: Thomas Huth <thuth@redhat.com> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>