In particular this simplifies the &s->mpu->cpu->env expression again.

first_cpu and ->next_cpu are expected to be QOM'ified later.
Signed-off-by: NAndreas Färber <afaerber@suse.de>
Acked-by: Igor Mitsyanko <i.mitsyanko@samsung.com> (for exynos)
Acked-by: NPeter Maydell <peter.maydell@linaro.org>