iommu/omap: Integrate omap-iommu-debug into omap-iommu

The debugfs support for OMAP IOMMU is currently implemented
as a module, warranting certain OMAP-specific IOMMU API to
be exported. The OMAP IOMMU, when enabled, can only be built-in
into the kernel, so integrate the OMAP IOMMU debug module
into the OMAP IOMMU driver. This helps in eliminating the
need to export most of the current OMAP IOMMU API.

The following are the main changes:
- The debugfs directory and entry creation logic is reversed,
  the calls are invoked by the OMAP IOMMU driver now.
- The current iffy circular logic of adding IOMMU archdata
  to the IOMMU devices itself to get a pointer to the omap_iommu
  object in the debugfs support code is replaced by directly
  using the omap_iommu structure while creating the debugfs
  entries.
- The debugfs root directory is renamed from the generic name
  "iommu" to a specific name "omap_iommu".
- Unneeded headers have also been cleaned up while at this.
- There will no longer be a omap-iommu-debug.ko module after
  this patch.
- The OMAP_IOMMU_DEBUG Kconfig option is converted to boolean
  only, the OMAP IOMMU debugfs support is built alongside the
  OMAP IOMMU driver only when this option is enabled.

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>