ARM: OMAP2+: Move iommu2 to drivers/iommu/omap-iommu2.c

This file should not be in arch/arm. Move it to drivers/iommu
to allow making most of the header local to drivers/iommu.

This is needed as we are removing plat and mach includes
from drivers for ARM common zImage support.

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