iommu/omap: Move debugfs functions to omap-iommu-debug.c

The main OMAP IOMMU driver file has some helper functions used
by the OMAP IOMMU debugfs functionality, and there is already a
dedicated source file omap-iommu-debug.c dealing with these debugfs
routines. Move all these functions to the omap-iommu-debug.c file,
so that all the debugfs related routines are in one place.

The move required exposing some new functions and moving some
definitions to the internal omap-iommu.h header file.

Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>