omap: iommu: migrate to the generic IOMMU API

Migrate OMAP's iommu driver to the generic IOMMU API, so users can stay
generic, and any generic IOMMU functionality can be developed once
in the generic framework.

Migrate omap's iovmm (virtual memory manager) to the generic IOMMU API,
and adapt omap3isp as needed, so the latter won't break.

The plan is to eventually remove iovmm completely by replacing it
with the (upcoming) IOMMU-based DMA-API.

Tested on OMAP3 (with omap3isp) and OMAP4 (with rpmsg/remoteproc).

Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hiroshi DOYU <Hiroshi.DOYU@nokia.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>