Prepend 'omap_' to OMAP's 'struct iommu' and exposed API, to prevent
namespace pollution and generally to improve readability of the code
that still uses the driver directly.

Update the users as needed as well.
Signed-off-by: NOhad Ben-Cohen <ohad@wizery.com>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: NHiroshi DOYU <Hiroshi.DOYU@nokia.com>
Acked-by: NTony Lindgren <tony@atomide.com>
Signed-off-by: NJoerg Roedel <joerg.roedel@amd.com>