iommu/arm: Add support for ARM Ltd. System MMU architecture

This patch adds support for SMMUs implementing the ARM System MMU
architecture versions 1 or 2. Both arm and arm64 are supported, although
the v7s descriptor format is not used.

Cc: Rob Herring <robherring2@gmail.com>
Cc: Andreas Herrmann <andreas.herrmann@calxeda.com>
Cc: Olav Haugan <ohaugan@codeaurora.org>
Cc: Joerg Roedel <joro@8bytes.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Andreas Herrmann <andreas.herrmann@calxeda.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>