omap: iovmm: remove unused functionality

Remove unused functionality from OMAP's iovmm module.

The intention is to eventually completely replace iovmm with the
generic DMA-API, so new code that'd need this iovmm functionality
will have to extend the DMA-API instead.

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>