x86, mm: Prepare zone_sizes_init() for unification

Make 32-bit and 64-bit zone_sizes_init() identical in
preparation for unification.

Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
Link: http://lkml.kernel.org/r/1320155902-10424-6-git-send-email-penberg@kernel.org


Signed-off-by: Ingo Molnar <mingo@elte.hu>