iommu/omap: Remove omap_iommu_arch_version() and version field

The function omap_iommu_arch_version() is not used anymore,
and is not required either, so remove it. The .version field
in struct iommu_functions that this function uses is also
removed, as it is not really an ops to retrieve a version and
there won't be any usage for this field either.

Signed-off-by: Suman Anna <s-anna@ti.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>