arm64: device: add iommu pointer to device archdata

arm64: device: add iommu pointer to device archdata

When using an IOMMU for device mappings, it is necessary to keep a
pointer between the device and the IOMMU to which it is attached in
order to obtain the correct IOMMU when attaching the device to a domain.

This patch adds an iommu pointer to the dev_archdata structure, in a
similar manner to other architectures (ARM, PowerPC, x86, ...).

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit 73150c983ac1f9b7653cfd3823b1ad4a44aad3bf)
Signed-off-by: Mark Brown <broonie@linaro.org>