A client user instantiates and attaches to an iommu_domain to
program the OMAP IOMMU associated with the domain. The iommus
programmed by a client user are bound with the iommu_domain
through the user's device archdata. The OMAP IOMMU driver
currently supports only one IOMMU per IOMMU domain per user.

The OMAP IOMMU driver has been enhanced to support allowing
multiple IOMMUs to be programmed by a single client user. This
support is being added mainly to handle the DSP subsystems on
the DRA7xx SoCs, which have two MMUs within the same subsystem.
These MMUs provide translations for a processor core port and
an internal EDMA port. This support allows both the MMUs to
be programmed together, but with each one retaining it's own
internal state objects. The internal EDMA block is managed by
the software running on the DSPs, and this design provides
on-par functionality with previous generation OMAP DSPs where
the EDMA and the DSP core shared the same MMU.

The multiple iommus are expected to be provided through a
sentinel terminated array of omap_iommu_arch_data objects
through the client user's device archdata. The OMAP driver
core is enhanced to loop through the array of attached
iommus and program them for all common operations. The
sentinel-terminated logic is used so as to not change the
omap_iommu_arch_data structure.

NOTE:
1. The IOMMU group and IOMMU core registration is done only for
   the DSP processor core MMU even though both MMUs are represented
   by their own platform device and are probed individually. The
   IOMMU device linking uses this registered MMU device. The struct
   iommu_device for the second MMU is not used even though memory
   for it is allocated.
2. The OMAP IOMMU debugfs code still continues to operate on
   individual IOMMU objects.
Signed-off-by: Suman Anna <s-anna@ti.com>
[t-kristo@ti.com: ported support to 4.13 based kernel]
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>