iommu/omap: Remove virtual memory manager

The OMAP3 ISP driver was the only user of the OMAP IOVMM API. Now that
is has been ported to the DMA API, remove the unused virtual memory
manager.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>