omap: iommu: remove unused exported API

Remove unused public APIs from OMAP's iommu driver.

IOMMU functionality should be exposed only via the generic IOMMU API;
this way drivers stay generic, and different IOMMU drivers
don't need to duplicate similar functionalities.

The rest of the API still exposed by OMAP's iommu will be evaluated
and eventually either added to the generic IOMMU API (if relevant),
or completely removed.

The intention is that OMAP's iommu driver will eventually not expose
any public API.

Signed-off-by: Ohad Ben-Cohen <ohad@wizery.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>