ARM: OMAP2+: Move plat/iovmm.h to include/linux/omap-iommu.h

Looks like the iommu framework does not have generic functions
exported for all the needs yet. The hardware specific functions
are defined in files like intel-iommu.h and amd-iommu.h. Follow
the same standard for omap-iommu.h.

This is needed because we are removing plat and mach includes
for ARM common zImage support. Further work should continue
in the iommu framework context as only pure platform data will
be communicated from arch/arm/*omap*/* code to the iommu
framework.

Cc: Ido Yariv <ido@wizery.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Omar Ramirez Luna <omar.luna@linaro.org>
Cc: linux-media@vger.kernel.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>