ARM: OMAP: Merge iommu2.h into iommu.h

Since iommu is not supported on OMAP1 and will not likely to ever be
supported, merge plat/iommu2.h into iommu.h so only one file would have
to move to platform_data/ as part of the single zImage effort.

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