iommu/omap: Fix build error with !IOMMU_SUPPORT

Without this patch it is possible to select the VIDEO_OMAP3
driver which then selects OMAP_IOVMM. But the omap iommu
driver is not compiled without IOMMU_SUPPORT enabled. Fix
that by forcing OMAP_IOMMU and OMAP_IOVMM are enabled before
VIDEO_OMAP3 can be selected.

Cc: Ohad Ben-Cohen <ohad@wizery.com>
Cc: iommu@lists.linux-foundation.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>