Move iommu/iovmm headers from plat/ to platform_data/ as part of the
single zImage work.

Partially based on an earlier version by Ido Yariv <ido@wizery.com>.

Cc: Ido Yariv <ido@wizery.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Omar Ramirez Luna <omar.luna@linaro.org>
Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Acked-by: Ohad Ben-Cohen <ohad@wizery.com>
Acked-by: Joerg Roedel <joro@8bytes.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>